Wild-type Lungs Research Articles

7. Lentiviral Vector-Mediated CFTR Gene Transfer to CF Pig Airways Corrects the Anion Transport Defect In Vivo

Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasian populations and is caused by mutations in CFTR. Complementation of CFTR rescues the anion transport defect in vitro, making this monogenetic disease a candidate for CF gene therapy. Lentiviral vector-mediated CFTR gene transfer has long been discussed as a promising strategy for gene therapy. Lentiviral vectors can efficiently transduce non-dividing cells and persistently express a therapeutic transgene. We previously demonstrated that the non-primate lentiviral vector derived from feline immunodeficiency virus (FIV) and pseudotyped with a GP64 envelope confers gene transfer to porcine airway epithelia both in well-differentiated primary cultures in vitro and in wild-type pig lungs in vivo. The CF pig model recapitulates many features of human disease and provides a new platform for preclinical gene therapy studies. Here, we show that lentiviral-mediated delivery of CFTR to nasal and lung epithelia corrects the anion channel defect in the CF pig model. We delivered GP64-FIV-pigCFTR to the nose and lung of 2-week old gut-corrected CF pigs using a MADgic atomizer. Two weeks post-transduction, we harvested sinus, trachea, and bronchus tissue to assay for gene correction. In freshly excised trachea and bronchus tissue explants, we observed a short-circuit current response to forskolin and IBMX (F&I) and inhibition by GlyH-101, consistent with CFTR function. Compared to non-transduced animals, cultured ethmoid sinus epithelia also showed evidence of correction by short-circuit current measurements. Loss of CFTR results in reduced bicarbonate transport and a lower ASL pH. A reduction in ASL pH impairs bacterial killing. Following gene transfer, we observed an increase in nasal and tracheal pH and rescue of bacterial killing. Together, these exciting results demonstrate the first evidence of functional in vivo correction of CFTR by a lentivirus in the CF pig model. These findings support the utility of a lentivirus for CF gene therapy.

Adaptation of seasonal influenza virus H1N1 and H3N2 vaccine strains in BALB/c mouse pneumonitis model

Objective To investigate the possibility of adaptation seasonal influenza virus H1N1 and H3N2 vaccine strains in BALB/C mice. Methods BALB/c mice were infected with wild-type virus and lungs were dissected out at peak of virus multiplication to generate the first passage of mouse adapted virus (P1), which was subjected serial mouse lung-to-lung passages (from P1 to P10). Pathogenicity and genome sequences of wide-type and mouse-adapted virus were compared. Results For H3N2 vaccine strain, virus titer was under detection at any passages. In contrast, for H1N1 vaccine strain, virus replication ability and pathogenicity increased by lung-to-lung passage. Genome sequence analysis of H1N1wt and H1N1MA indicated that mutation of HA-N142D contributed to the enhanced virulence. Conclusions H3N2 vaccine strain was difficult to replicate in mice while H1N1 vaccine strain could effectively replicate in BALB/c mice and mutation of HA-N142D contributed to the enhanced virulence. Key words: Influenza A virus; Influenza vaccine; Mice, inbred BALB C

Stromal matrix metalloproteinase 2 regulates collagen expression and promotes the outgrowth of experimental metastases.

Breast cancer survival rates decrease from 99% for patients with local disease to 25% for those with distant metastases. Matrix metalloproteinases (MMPs), including MMP2, are associated with metastatic progression. We found that loss of host MMP2 reduces the proliferation of experimental metastases in the lungs and identified fibroblasts in tumour-bearing lungs as the major source of MMP2. In vitro, spheroidal mammary tumour growth was increased by co-culture with control fibroblasts isolated from tumour-bearing lungs, but not when fibroblasts with stable Mmp2 knockdown were used. This result prompted us to assess whether MMP2 was responsible for a tumour-proliferative, activated fibroblast phenotype. To test this, we evaluated: (a) fibroblasts from wild-type tumour-bearing lungs, with or without shRNA-mediated MMP2 knockdown; and (b) normal, quiescent fibroblasts isolated from either WT or Mmp2(-/-) mice. Quantitative PCR revealed that Mmp2 knockdown attenuated expression of two markers of activation (α-smooth muscle actin and vimentin), but there was minimal expression in quiescent WT or Mmp2(-/-) fibroblasts, as expected. Placing quiescent fibroblasts under activating conditions led to increases in activation-associated transcripts in WT but not Mmp2(-/-) fibroblasts. Additionally, Mmp2 knockdown fibroblasts showed significantly decreased expression of the matrix transcripts collagen I, collagen IV and fibronectin. Addition of active TGFβ was sufficient to rescue the MMP2-dependent collagen I and IV expression, while MMP2-induced collagen expression was blocked by the addition of TGFβ1-neutralizing antibody. Gene expression data in stromal cells of human breast cancers reveal that MMP2 expression is also positively correlated with activation and matrix transcripts. Thus, we present a model whereby MMP2 production in tumour fibroblasts is important for TGFβ1 activity and subsequent activation of fibroblasts to a matrix-producing, proliferation-supportive phenotype. Overall, our results reveal a previously undefined role for MMP2 in metastatic outgrowth mediated by fibroblasts, and extend the mechanisms by which MMPs contribute to tumour progression.

Repression of Igf1 expression by Ezh2 prevents basal cell differentiation in the developing lung.

Epigenetic mechanisms involved in the establishment of lung epithelial cell lineage identities during development are largely unknown. Here, we explored the role of the histone methyltransferase Ezh2 during lung lineage determination. Loss of Ezh2 in the lung epithelium leads to defective lung formation and perinatal mortality. We show that Ezh2 is crucial for airway lineage specification and alveolarization. Using optical projection tomography imaging, we found that branching morphogenesis is affected in Ezh2 conditional knockout mice and the remaining bronchioles are abnormal, lacking terminally differentiated secretory club cells. Remarkably, RNA-seq analysis revealed the upregulation of basal genes in Ezh2-deficient epithelium. Three-dimensional imaging for keratin 5 further showed the unexpected presence of a layer of basal cells from the proximal airways to the distal bronchioles in E16.5 embryos. ChIP-seq analysis indicated the presence of Ezh2-mediated repressive marks on the genomic loci of some but not all basal genes, suggesting an indirect mechanism of action of Ezh2. We found that loss of Ezh2 de-represses insulin-like growth factor 1 (Igf1) expression and that modulation of IGF1 signaling ex vivo in wild-type lungs could induce basal cell differentiation. Altogether, our work reveals an unexpected role for Ezh2 in controlling basal cell fate determination in the embryonic lung endoderm, mediated in part by repression of Igf1 expression.

The putative tumor suppressor gene EphA3 fails to demonstrate a crucial role in murine lung tumorigenesis or morphogenesis.

Treatment of non-small cell lung cancer (NSCLC) is based on histological analysis and molecular profiling of targetable driver oncogenes. Therapeutic responses are further defined by the landscape of passenger mutations, or loss of tumor suppressor genes. We report here a thorough study to address the physiological role of the putative lung cancer tumor suppressor EPH receptor A3 (EPHA3), a gene that is frequently mutated in human lung adenocarcinomas. Our data shows that homozygous or heterozygous loss of EphA3 does not alter the progression of murine adenocarcinomas that result from Kras mutation or loss of Trp53, and we detected negligible postnatal expression of EphA3 in adult wild-type lungs. Yet, EphA3 was expressed in the distal mesenchyme of developing mouse lungs, neighboring the epithelial expression of its Efna1 ligand; this is consistent with the known roles of EPH receptors in embryonic development. However, the partial loss of EphA3 leads only to subtle changes in epithelial Nkx2-1, endothelial Cd31 and mesenchymal Fgf10 RNA expression levels, and no macroscopic phenotypic effects on lung epithelial branching, mesenchymal cell proliferation, or abundance and localization of CD31-positive endothelia. The lack of a discernible lung phenotype in EphA3-null mice might indicate lack of an overt role for EPHA3 in the murine lung, or imply functional redundancy between EPHA receptors. Our study shows how biological complexity can challenge in vivo functional validation of mutations identified in sequencing efforts, and provides an incentive for the design of knock-in or conditional models to assign the role of EPHA3 mutation during lung tumorigenesis.

Abstract 17301: Increased Pulmonary Vascular and Systemic Response to Chronic Hypoxia in Sirtuin 1 Mutant Mice: a Role for Hypoxia-inducible Factor-3α?

Introduction: Pulmonary Hypertension is caused by occlusive remodelling of pulmonary arterioles leading to increased pulmonary vascular resistance, right ventricle hypertrophy and eventually failure. Sirtuin-1 (Sirt1) is an NAD+-dependent deacetylase that has been strongly implicated in endothelium homeostasis in systemic vessels, but little is known about its role in hypoxia sensing. Hypothesis: We assessed the hypothesis that absence of Sirt1 catalytic activity is detrimental to the hypoxic response in mice. Methods: Mice lacking Sirt1 catalytic activity (sirt1Y/Y, H355Y) and their wild type (WT) littermates were exposed to chronic hypoxia (10% O2) for 1, 7 or 21 days. Results: Sirt1Y/Y exhibited an exaggerated increase in right ventricle systolic pressure, apparent within the first week of hypoxic exposure, which progressively increased over the 3 week CH exposure period (42±2 sirt1Y/Y vs. 30±1 WT; n=27/group, p< 0.001). Right ventricular hypertrophy, assessed by the RV/LV+S weight ratio, was also increased (Day 21: 0.56±0.01 sirt1Y/Y vs. 0.43±0.01 WT, n=27/group; p< 0.001). Hemtaocrit levels were similar in Sirt1Y/Y and WT mice at baseline; however, there was a delayed increase after three weeks of CH in Sirt1Y/Y mice relative to WT mice (71±2% sirt1Y/Y vs. 63±1% WT, n=17/group; p<0.001). Plasma levels of erythropoietin (EPO), assessed by ELISA at each time point, were markedly increased at Day 7 in Sirt1Y/Y vs. WT mice (492±240 vs. 81±16pg/mL, respectively; n=7-9, p< 0.05) but normalized at later time points (Day 21: 75±9 sirt1Y/Y vs. 96±12pg/mL WT; n=4/group). Surprisingly, expression of both HIF1α and 2α mRNA was decreased in mutant mice lungs during chronic hypoxia at all time points, as was the expression of several HIF1/2α responsive target genes. However, there was a dramatic increase in HIF3α in Sirt1 mutant vs. WT lungs, which has been implicated both in repression of other HIFs as well as in directly mediating hypoxic signaling. Conclusions: Loss of Sirt-1 deacetylation activity led to an exaggerated pulmonary and systemic response to hypoxia, consistent with a role for Sirt1 in hypoxia sensing and/or signaling. As well, our data suggest that HIF3α is a novel downstream target for Sirt1 in the regulation of the response to chronic hypoxia.

SIRTUIN 1 PLAYS A CRUCIAL ROLE IN MODULATING THE PULMONARY AND SYSTEMIC HYPOXIC RESPONSE IN MICE: NOVEL ROLE FOR HYPOXIA INDUCIBLE FACTOR-3ALPHA?

BACKGROUND: Pulmonary Hypertension (PH) is caused by occlusive remodelling of pulmonary arterioles leading to increased pulmonary vascular resistance, right ventricle hypertrophy and eventually failure. Sirtuin (Sirt)-1 is an NAD+-dependent deacetylase that has been strongly implicated in maintaining endothelium homeostasis in systemic vessels, but little is known about its role in hypoxia sensing and the lung vasculature. Thus, the goal of this study was to understand the mechanisms by which Sirt1 regulates the pulmonary vascular and systemic response to chronic hypoxia (CH)-induced PH. METHODS AND RESULTS: Mice lacking Sirt1 catalytic activity (sirt1Y/Y, H355Y) and their wild type (WT) littermates were exposed to chronic hypoxia (10% O2) for 1, 7, 14 or 21 days. Sirt1Y/Y exhibited an exaggerated increase in right ventricle systolic pressure (RVSP), apparent within the first week of hypoxic exposure (Day 7: 33 2 sirt1Y/Y vs. 27 2 WT; n1⁄48-10, p< 0.05) which progressively increased over the 3 week CH exposure period (41.5 1.8 sirt1Y/Y vs. 29.7 0.8 WT; n1⁄427 both, p< 0.001). Right ventricular (RV) hypertrophy, assessed by the RV/LV+S weight ratio was also increased (Day 7: 0.52 0.01 sirt1Y/Y vs. 0.40 0.02 WT, n1⁄48-10; p< 0.0001). Hemtaocrit levels were similar in Sirt1Y/Y and WT mice at baseline; however, there was a delayed increase after three weeks of CH in Sirt1Y/Y mice relative to WT mice (Day 7: 55 2% sirt1Y/Y vs. 52 2% WT, n1⁄48-9) (Day 21: 71 2% sirt1Y/Y vs. 63 1% WT, n1⁄417 both; p<0.001). Plasma levels of erythropoietin (EPO), a hypoxic responsive protein responsible for hematopoiesis, were assessed by ELISA at each time point. EPO was markedly increased at Day 7 in Sirt1Y/Y vs. WT mice (492 240 vs. 81 16pg/mL, respectively; n1⁄47-9, p< 0.05) but normalized at later time points (Day 21: 75 9 sirt1Y/Y vs. 96 12pg/mL WT; n1⁄44 both). Lung expression of the hypoxia inducible factors (HIF) 1a and 2a subunits was not increased by western blot analysis. Moreover, HIF1a and HIF2a responsive target genes showed no increase in transcript levels. However, there was a dramatic increase in HIF3a expression in Sirt1 mutant vs. WT lungs, which has been implicated both in repression of other HIFs transcription, activity as well as a direct mediator hypoxic signaling. CONCLUSION: Our data supports a role for Sirt1 in modulating the response to hypoxia, with loss of deacetylation activity leading to an exaggerated pulmonary and systemic induction of the hypoxic response genes.This appears to bemediatedbyHIF3a as a potential novel downstream target for Sirt1 activity in hypoxia. CIHR

Chitinase-3 like-protein-1 (CHI3L1) expression associated with pulmonary inflammation accelerates breast cancer metastasis (TUM7P.960)

Abstract Disseminated metastasis accounts for a majority of breast cancer deaths. Recently, elevated serum levels of a glycoprotein known as chitinase-3 like-protein-1 (CHI3L1) has been correlated with poor prognosis in both breast cancer and asthmatic patients. We have combined mouse models of breast cancer and pulmonary inflammation to determine if CHI3L1 associated pulmonary inflammation accelerates metastasis. We found that allergic pulmonary inflammation significantly enhances primary tumor growth in 4T1, 4T07 and 67NR mammary tumors by 10-fold, while decreasing survival. 4T1 tumor bearers with allergic pulmonary inflammation showed a 100-fold increase in metastatic tumor formation. We also assessed CHI3L1 levels and myeloid cells in the lungs of wild type and CHI3L1 knockout mice with allergic pulmonary inflammation and 4T1 mammary tumors. CHI3L1 levels were higher in the lungs of mammary tumor bearers with allergic pulmonary inflammation and correlated with increased metastasis. Wild type mammary tumor bearers with allergic inflammation had higher numbers of myeloid cells in the lungs in comparison to CHI3L1 knockout tumor bearers with allergic pulmonary inflammation. CHI3L1 knockout mice tumor bearers had significantly fewer myeloid cells in the lungs, decreased tumor growth and metastasis, along with increased survival. We propose that increased CHI3L1 in the lungs attracts myeloid cells that promote tumor growth and breast cancer metastasis.

ATF3 is a novel regulator of mouse neutrophil migration

AbstractExpression of the activating transcription factor 3 (ATF3) gene is induced by Toll-like receptor (TLR) signaling. In turn, ATF3 protein inhibits the expression of various TLR-driven proinflammatory genes. Given its counter-regulatory role in diverse innate immune responses, we defined the effects of ATF3 on neutrophilic airway inflammation in mice. ATF3 deletion was associated with increased lipopolysaccharide (LPS)-driven airway epithelia production of CXCL1, but not CXCL2, findings concordant with a consensus ATF3-binding site identified solely in the Cxcl1 promoter. Unexpectedly, ATF3-deficient mice did not exhibit increased airway neutrophilia after LPS challenge. Bone marrow chimeras revealed a specific reduction in ATF3−/− neutrophil recruitment to wild-type lungs. In vitro, ATF3−/− neutrophils exhibited a profound chemotaxis defect. Global gene expression analysis identified ablated Tiam2 expression in ATF3−/− neutrophils. TIAM2 regulates cellular motility by activating Rac1-mediated focal adhesion disassembly. Notably, ATF3−/− and ATF3-sufficient TIAM2 knockdown neutrophils, both lacking TIAM2, exhibited increased focal complex area, along with excessive CD11b-mediated F-actin polymerization. Together, our data describe a dichotomous role for ATF3-mediated regulation of neutrophilic responses: inhibition of neutrophil chemokine production but promotion of neutrophil chemotaxis.

JNK suppresses pulmonary fibroblast elastogenesis during alveolar development

BackgroundThe formation of discrete elastin bands at the tips of secondary alveolar septa is important for normal alveolar development, but the mechanisms regulating the lung elastogenic program are incompletely understood. JNK suppress elastin synthesis in the aorta and is important in a host of developmental processes. We sought to determine whether JNK suppresses pulmonary fibroblast elastogenesis during lung development.MethodsAlveolar size, elastin content, and mRNA of elastin-associated genes were quantitated in wild type and JNK-deficient mouse lungs, and expression profiles were validated in primary lung fibroblasts. Tropoelastin protein was quantitated by Western blot. Changes in lung JNK activity throughout development were quantitated, and pJNK was localized by confocal imaging and lineage tracing.ResultsBy morphometry, alveolar diameters were increased by 7% and lung elastin content increased 2-fold in JNK-deficient mouse lungs compared to wild type. By Western blot, tropoelastin protein was increased 5-fold in JNK-deficient lungs. Postnatal day 14 (PND14) lung JNK activity was 11-fold higher and pJNK:JNK ratio 6-fold higher compared to PN 8 week lung. Lung tropoelastin, emilin-1, fibrillin-1, fibulin-5, and lysyl oxidase mRNAs inversely correlated with lung JNK activity during alveolar development. Phosphorylated JNK localized to pulmonary lipofibroblasts. PND14 JNK-deficient mouse lungs contained 7-fold more tropoelastin, 2,000-fold more emilin-1, 800-fold more fibrillin-1, and 60-fold more fibulin-5 than PND14 wild type lungs. Primarily lung fibroblasts from wild type and JNK-deficient mice showed similar differences in elastogenic mRNAs.ConclusionsJNK suppresses fibroblast elastogenesis during the alveolar stage of lung development.

SerpinB1 deficiency is not associated with increased susceptibility to pulmonary emphysema in mice

Chronic obstructive pulmonary disease (COPD) is characterized by emphysema and chronic bronchitis and is a leading cause of morbidity and mortality worldwide. Tobacco smoke and deficiency in α1-antitrypsin (AAT) are the most prominent environmental and genetic risk factors, respectively. Yet the pathogenesis of COPD is not completely elucidated. Disease progression appears to include a vicious circle driven by self-perpetuating lung inflammation, endothelial and epithelial cell death, and proteolytic degradation of extracellular matrix proteins. Like AAT, serpinB1 is a potent inhibitor of serine proteases including neutrophil elastase and cathepsin G. Because serpinB1 is expressed in myeloid and lung epithelial cells and is protective during lung infections, we investigated the role of serpinB1 in preventing age-related and cigarette smoke-induced emphysema in mice. Fifteen-month-old mice showed increased lung volume and decreased pulmonary function compared with young adult mice (3 mo old), but no differences were observed between serpinB1-deficient (KO) and wild-type (WT) mice. Chronic exposure to secondhand cigarette smoke resulted in structural emphysematous changes compared with respective control mice, but no difference in lung morphometry was observed between genotypes. Of note, the different pattern of stereological changes induced by age and cigarette smoke suggest distinct mechanisms leading to increased airway volume. Finally, expression of intracellular and extracellular protease inhibitors were differently regulated in lungs of WT and KO mice following smoke exposure; however, activity of proteases was not significantly altered. In conclusion, we showed that, although AAT and serpinB1 are similarly potent inhibitors of neutrophil proteases, serpinB1 deficiency is not associated with more severe emphysema.

Bacterial Pathogens Activate a Common Inflammatory Pathway through IFNλ Regulation of PDCD4

The type III interferon (IFNλ) receptor IL-28R is abundantly expressed in the respiratory tract and has been shown essential for host defense against some viral pathogens, however no data are available concerning its role in the innate immune response to bacterial pathogens. Staphylococcus aureus and Pseudomonas aeruginosa induced significant production of IFNλ in the lung, and clearance of these bacteria from the lung was significantly increased in IL-28R null mice compared to controls. Improved bacterial clearance correlated with reduced lung pathology and a reduced ratio of pro- vs anti-inflammatory cytokines in the airway. In human epithelial cells IFNλ inhibited miR-21 via STAT3 resulting in upregulation of PDCD4, a protein known to promote inflammatory signaling. In vivo 18 hours following infection with either pathogen, miR-21 was significantly reduced and PDCD4 increased in the lungs of wild type compared to IL-28R null mice. Infection of PDCD4 null mice with USA300 resulted in improved clearance, reduced pathology, and reduced inflammatory cytokine production. These data suggest that during bacterial pneumonia IFNλ promotes inflammation by inhibiting miR-21 regulation of PDCD4.

PECAM-1 and caveolae form the mechanosensing complex necessary for NOX2 activation and angiogenic signaling with stopped flow in pulmonary endothelium.

We showed that stop of flow triggers a mechanosignaling cascade that leads to the generation of reactive oxygen species (ROS); however, a mechanosensor coupled to the cytoskeleton that could potentially transduce flow stimulus has not been identified. We showed a role for KATP channel, caveolae (caveolin-1), and NADPH oxidase 2 (NOX2) in ROS production with stop of flow. Based on reports of a mechanosensory complex that includes platelet endothelial cell adhesion molecule-1 (PECAM-1) and initiates signaling with mechanical force, we hypothesized that PECAM-1 could serve as a mechanosensor in sensing disruption of flow. Using lungs in situ, we observed that ROS production with stop of flow was significantly reduced in PECAM-1(-/-) lungs compared with lungs from wild-type (WT) mice. Lack of PECAM-1 did not affect NOX2 activation machinery or the caveolin-1 expression or caveolae number in the pulmonary endothelium. Stop of flow in vitro triggered an increase in angiogenic potential of WT pulmonary microvascular endothelial cells (PMVEC) but not of PECAM-1(-/-) PMVEC. Obstruction of flow in lungs in vivo showed that the neutrophil infiltration as observed in WT mice was significantly lowered in PECAM-1(-/-) mice. With stop of flow, WT lungs showed higher expression of the angiogenic marker VEGF compared with untreated (sham) and PECAM-1(-/-) lungs. Thus PECAM-1 (and caveolae) are parts of the mechanosensing machinery that generates superoxide with loss of shear; the resultant ROS potentially drives neutrophil influx and acts as an angiogenic signal.

Sustained function of genetically modified porcine lungs in an ex vivo model of pulmonary xenotransplantation

Xenotransplantation could provide a solution to the donor shortage that is currently the major barrier to solid-organ transplantation. The ability to breed pigs with multiple genetic modifications provides a unique opportunity to explore the immunologic challenges of pulmonary xenotransplantation. Explanted lungs from wild-type and 3 groups of genetically modified pigs were studied: (i) α1,3-galactosyltransferase gene knockout (GTKO); (ii) GTKO pigs expressing the human complementary regulatory proteins CD55 and CD59 (GTKO/CD55-59); and (iii) GTKO pigs expressing both CD55-59 and CD39 (GTKO/CD55-59/CD39). The physiologic, immunologic and histologic properties of porcine lungs were evaluated on an ex vivo rig after perfusion with human blood. Lungs from genetically modified pigs demonstrated stable pulmonary vascular resistance and better oxygenation of the perfusate, and survived longer than wild-type lungs. Physiologic function was inversely correlated with the degree of platelet sequestration into the xenograft. Despite superior physiologic profiles, lungs from genetically modified pigs still showed evidence of intravascular thrombosis and coagulopathy after perfusion with human blood. The ability to breed pigs with multiple genetic modifications, and to evaluate lung physiology and histology in real-time on an ex vivo rig, represent significant advances toward better understanding the challenges inherent to pulmonary xenotransplantation.

A Protective Hsp70–TLR4 Pathway in Lethal Oxidant Lung Injury

Administering high levels of inspired oxygen, or hyperoxia, is commonly used as a life-sustaining measure in critically ill patients. However, prolonged exposures can exacerbate respiratory failure. Our previous study showed that TLR4 confers protection against hyperoxia-induced lung injury and mortality. Hsp70 has potent cytoprotective properties and has been described as a TLR4 ligand in cell lines. We sought to elucidate the relationship between TLR4 and Hsp70 in hyperoxia-induced lung injury in vitro and in vivo and to define the signaling mechanisms involved. Wild-type, TLR4(-/-), and Trif(-/-) (a TLR4 adapter protein) murine lung endothelial cells (MLECs) were exposed to hyperoxia. We found markedly elevated levels of intracellular and secreted Hsp70 from wild-type mice lungs and MLECs after hyperoxia. We confirmed that Hsp70 and TLR4 coimmunoprecipitate in lung tissue and MLECs. Hsp70-mediated NF-κB activation appears to depend upon TLR4. In the absence of TLR4, Hsp70 loses its protective effects in endothelial cells. Furthermore, these protective properties of Hsp70 are TLR4 adapter Trif dependent and MyD88 independent. Hsp70-deficient mice have increased mortality during hyperoxia, and lung-targeted adenoviral delivery of Hsp70 effectively rescues both Hsp70-deficient and wild-type mice. To our knowledge, our studies are the first to define an Hsp70-TLR4-Trif cytoprotective axis in the lung and endothelial cells. This pathway is a potential therapeutic target against a range of oxidant-induced lung injuries.

Mice deficient in the St3gal3 gene product α2,3 sialyltransferase (ST3Gal-III) exhibit enhanced allergic eosinophilic airway inflammation

Sialic acid-binding immunoglobulin-like lectin (Siglec)-F is a proapoptotic receptor on mouse eosinophils, but little is known about its natural tissue ligand. We previously reported that the St3gal3 gene product α2,3 sialyltransferase (ST3Gal-III) is required for constitutive Siglec-F lung ligand synthesis. We therefore hypothesized that attenuation of ST3Gal-III will decrease Siglec-F ligand levels and enhance allergic eosinophilic airway inflammation. C57BL/6 wild-type mice and St3gal3 heterozygous or homozygous deficient (St3gal3(+/-) and St3gal3(-/-)) mice were used. Eosinophilic airway inflammation was induced through sensitization to ovalbumin (OVA) and repeated airway OVA challenge. Siglec-F human IgG1 fusion protein (Siglec-F-Fc) was used to detect Siglec-F ligands. Lung tissue and bronchoalveolar lavage fluid (BALF) were analyzed for inflammation, as well as various cytokines and chemokines. Serum was analyzed for allergen-specific immunoglobulin levels. Western blotting with Siglec-F-Fc detected approximately 500-kDa and approximately 200-kDa candidate Siglec-F ligands that were less abundant in St3gal3(+/-) lung extracts and nearly absent in St3gal3(-/-) lung extracts. After OVA sensitization and challenge, Siglec-F ligands were increased in wild-type mouse lungs but less so in St3gal3 mutants, whereas peribronchial and BALF eosinophil numbers were greater in the mutants, with the following rank order: St3gal3(-/-) ≥ St3gal3(+/-) > wild-type mice. Levels of various cytokines and chemokines in BALF were not significantly different among these 3 types of mice, although OVA-specific serum IgG1 levels were increased in St3gal3(-/-) mice. After OVA sensitization and challenge, St3gal3(+/-) and St3gal3(-/-) mice have more intense allergic eosinophilic airway inflammation and less sialylated Siglec-F ligands in their airways. One possible explanation for these findings is that levels of sialylated airway ligands for Siglec-F might be diminished in mice with attenuated levels of ST3Gal-III, resulting in a reduction in a natural proapoptotic pathway for controlling airway eosinophilia.

Kidney branching morphogenesis under the control of a ligand–receptor-based Turing mechanism

The main signalling proteins that control early kidney branching have been defined. Yet the underlying mechanism is still elusive. We have previously shown that a Schnakenberg-type Turing mechanism can recapitulate the branching and protein expression patterns in wild-type and mutant lungs, but it is unclear whether this mechanism would extend to other branched organs that are regulated by other proteins. Here, we show that the glial cell line-derived neurotrophic factor–RET regulatory interaction gives rise to a Schnakenberg-type Turing model that reproduces the observed budding of the ureteric bud from the Wolffian duct, its invasion into the mesenchyme and the observed branching pattern. The model also recapitulates all relevant protein expression patterns in wild-type and mutant mice. The lung and kidney models are both based on a particular receptor–ligand interaction and require (1) cooperative binding of ligand and receptor, (2) a lower diffusion coefficient for the receptor than for the ligand and (3) an increase in the receptor concentration in response to receptor–ligand binding (by enhanced transcription, more recycling or similar). These conditions are met also by other receptor–ligand systems. We propose that ligand–receptor-based Turing patterns represent a general mechanism to control branching morphogenesis and other developmental processes.

Circulating Fibrocytes Prepare the Lung for Cancer Metastasis by Recruiting Ly-6C+ Monocytes Via CCL2

Fibrocytes are circulating, hematopoietic cells that express CD45 and Col1a1. They contribute to wound healing and several fibrosing disorders by mechanisms that are poorly understood. In this report, we demonstrate that fibrocytes predispose the lung to B16-F10 metastasis by recruiting Ly-6C(+) monocytes. To do so, we isolated fibrocytes expressing CD45, CD11b, CD13, and Col1a1 from the lungs of wild type (WT) and Ccr5(-/-) mice. WT but not Ccr5(-/-) fibrocytes increased the number of metastatic foci when injected into Ccr5(-/-) mice (73 ± 2 versus 32 ± 5; p < 0.001). This process was MMP9 dependent. Injection of WT enhanced GFP(+) fibrocytes also increased the number of Gr-1(Int), CD11b(+), and enhanced GFP(-) monocytes. Like premetastatic-niche monocytes, these recruited cells expressed Ly-6C, CD117, and CD45. The transfer of these cells into Ccr5(-/-) mice enhanced metastasis (90 ± 8 foci) compared with B cells (27 ± 2), immature dendritic cells (31 ± 6), or alveolar macrophages (28 ± 3; p < 0.05). WT and Ccl2(-/-) fibrocytes also stimulated Ccl2 expression in the lung by 2.07 ± 0.05- and 2.78 ± 0.36-fold compared with Ccr5(-/-) fibrocytes (1.0 ± 0.06; p < 0.05). Furthermore, WT fibrocytes did not increase Ly-6C(+) monocytes in Ccr2(-/-) mice and did not promote metastasis in either Ccr2(-/-) or Ccl2(-/-) mice. These data support our hypothesis that fibrocytes contribute to premetastatic conditioning by recruiting Ly-6C(+) monocytes in a chemokine-dependent process. This work links metastatic risk to conditions that mobilize fibrocytes, such as inflammation and wound repair.

A Critical Regulatory Role for Macrophage Migration Inhibitory Factor in Hyperoxia-Induced Injury in the Developing Murine Lung

BackgroundThe role and mechanism of action of MIF in hyperoxia-induced acute lung injury (HALI) in the newborn lung are not known. We hypothesized that MIF is a critical regulatory molecule in HALI in the developing lung.MethodologyWe studied newborn wild type (WT), MIF knockout (MIFKO), and MIF lung transgenic (MIFTG) mice in room air and hyperoxia exposure for 7 postnatal (PN) days. Lung morphometry was performed and mRNA and protein expression of vascular mediators were analyzed.ResultsMIF mRNA and protein expression were significantly increased in WT lungs at PN7 of hyperoxia exposure. The pattern of expression of Angiopoietin 2 protein (in MIFKO>WT>MIFTG) was similar to the mortality pattern (MIFKO>WT>MIFTG) in hyperoxia at PN7. In room air, MIFKO and MIFTG had modest but significant increases in chord length, compared to WT. This was associated with decreased expression of Angiopoietin 1 and Tie 2 proteins in the MIFKO and MIFTG, as compared to the WT control lungs in room air. However, on hyperoxia exposure, while the chord length was increased from their respective room air controls, there were no differences between the 3 genotypes.ConclusionThese data point to the potential roles of Angiopoietins 1, 2 and their receptor Tie2 in the MIF-regulated response in room air and upon hyperoxia exposure in the neonatal lung.

Abstract 2875: NF-κB signaling in myeloid cells limits urethane-induced lung tumorigenesis.

Abstract The transcription factor Nuclear Factor κB (NF-κB) is a master regulator of inflammation, and its activation is associated with tumorigenesis in a variety of cancers. Our group has shown that NF-κB signaling in lung epithelial cells is critical for lung tumor formation. However, the role of NF-κB in other cell types, such as myeloid cells, during lung carcinogenesis is uncertain. We hypothesized that NF-κB signaling in myeloid cells (macrophages, monocytes, and neutrophils) promotes lung tumorigenesis by facilitating lung inflammation. Surprisingly, we found that mice with myeloid cell-targeted IKKβ deletion (IKKβΔmye mice) developed significantly more tumors than wild-type (WT) mice 4 months following a single intraperitoneal (IP) injection of the lung carcinogen urethane (1g/kg). IKKβΔmye mice exhibited a paradoxical increase in the proinflammatory cytokines IL-1β, TNFα, and CXCL1 at 1 and 2 weeks after urethane treatment, and a more than 3-fold higher influx of CD11b+Ly-6G+ cells into IKKβΔmye lungs compared to WT lungs was observed by flow cytometry 1 week post-urethane. By 6 weeks after urethane, IKKβΔmye mice developed more lung inflammation than WT mice, which was accompanied by an increased burden of atypical adenomatous hyperplasia lesions. Flow cytometric analysis of inflammatory cell populations at this time point revealed a sustained increase in granulocytic cells, indicated by significantly higher numbers of CD11b+Gr-1hi cells in the lungs of IKKβΔmye mice compared to WT mice. Depletion of granulocytic cells using Ly-6G antibody treatment (50ug/weekly IP injection) during the first 6 weeks of urethane-induced lung carcinogenesis reduced lung NF-κB activation and lung tumor incidence in IKKβΔmye mice to levels observed in urethane-treated WT mice, indicating that granulocytic cells play an important role in lung tumorigenesis during early tumor development and may do so by limiting NF-κB activation in lung epithelial cells. Together, our data suggest that the impact of NF-κB signaling on lung tumorigenesis is cell type specific and that myeloid NF-κB signaling limits urethane-induced inflammation and lung tumorigenesis. Granulocytes are important players during early lung tumor promotion, and we propose that they promote lung carcinogenesis through interactions that increase survival and/or proliferation of mutated lung epithelial cells. Citation Format: Allyson McLoed, Rinat Zaynagetdinov, Taylor Sherrill, Fiona Yull, Timothy Blackwell. NF-κB signaling in myeloid cells limits urethane-induced lung tumorigenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2875. doi:10.1158/1538-7445.AM2013-2875