Transforming growth factor-beta (TGFβ)-superfamily signaling has been implicated in the regulation of hepatocyte growth and regeneration after acute or chronic liver injury. However, the precise mechanisms underlying TGFβ signaling in the distinct hepatic cell types during the progression of liver fibrosis remain largely unknown. We aim to identify the downstream molecular mechanisms of TGFβ-signaling modulation on hepatocytes. To modulate TGFβ-superfamily signaling in vivo, Smad3 or Smad7 were adenovirally overexpressed in mouse liver. Parallelly, hepatosphere cultures were treated with recombinant TGFβ1 and subjected to transcriptomic analysis. These data were compared with transcriptomes from Smad7-overexpressing livers. To broaden the analysis, publicly available RNA-seq datasets from TGFβ-treated hepatic stellate cells and hepatocellular carcinoma lines were meta-analyzed. Finally, human liver tissues from cirrhotic and healthy individuals were examined for fibrosis and ribosome biogenesis markers to validate murine findings. Acute hepatic overexpression of Smad3 induced a transient fibrotic phenotype in the mouse liver. In hepatosphere cultures, TGFβ1 treatment suppressed key components of ribosomal assembly, whereas Smad7 overexpression exerted the opposite effect in the mouse liver, thus highlighting ribosome biogenesis as a major cellular process negatively regulated by the TGFβ superfamily. Inhibition of TGFβ signaling via Smad7 increased hepatic protein content (a critical parameter for restoring hepatic homeostasis upon liver damage), activated the nucleolus, and prompted the production of ribosomal pre-mRNAs without affecting p53 levels. Mechanistically, SMAD7-mediated inactivation of TGFβ signaling triggered selectively the p70S6K–S6RP regulatory axis, independently of cellular myelocytomatosis oncogene (c-MYC), mechanistic target of rapamycin (mTOR), and mitogen-activated protein kinase (MAPK) pathways. Importantly, analysis of hepatic tissue from cirrhotic patients and controls unveiled a negative association between TGFβ signaling and ribosome biogenesis in fibrotic livers. Complementary meta-analysis of RNA-seq data demonstrated that TGFβ regulates ribosome biogenesis in a cell type-specific manner, suppressing it in hepatocytes while enhancing it in hepatic stellate cells, consistent with their distinct functional states and transcriptional landscapes. Collectively, our data reveal a SMAD-dependent regulatory role of TGFβ-superfamily signaling on hepatocytes that is tightly connected with hepatic growth to ensure proper energy homeostasis and metabolism. This is a critical regeneration parameter, which is closely related to the restoration of hepatic mass, especially following liver injury and fibrosis.

Parkinson’s disease (PD) is characterized by the accumulation of alpha-synuclein (aSyn) aggregates in specific brain regions, which are likely to be the disease-causing entities. Herein, we employed novel, systemically administered, brain-penetrating viral vectors (PHP.eB AAVs) in order to evaluate the potential therapeutic utility of lowering the endogenous aSyn protein burden in the aSyn pre-formed fibril (PFF)-mouse model. Such vectors expressing short hairpin RNAs or micro RNAs targeting the mouse Snca transcript (or respective scrambled control sequences) were intravenously administered in adult wild-type mice and two weeks later human aSyn PFFs were injected into the dorsal striatum. Following the administration of the Snca-targeting PHP.eB AAVs, a successful widespread viral transduction was achieved throughout the brain, accompanied by an efficient reduction of endogenous aSyn protein levels within transduced dopaminergic neurons. Intrastriatal injection of human aSyn PFFs led to the formation of pSer129-aSyn-rich cytoplasmic inclusions in brain regions connected to the PFF-injection site, nigrostriatal degeneration and relevant behavioral motor deficits, at 2.5 months post PFF-injection. Importantly, PHP.eB AAV-mediated down-regulation of endogenous aSyn reduced the accumulation of pSer129-aSyn+ inclusions, mitigated nigrostriatal degeneration and alleviated motor impairments. Spread of pathology to other brain regions was also attenuated. Overall, such data highlight further the contribution of the intracellular aSyn protein load to the spread of pathology and suggest that this non-invasive delivery strategy holds promise in the research avenues for treating neurodegenerative diseases with widespread pathology, such as Synucleinopathies.

NLRP3‐driven inflammatory responses by circulating and lung‐resident monocytes are critical drivers of asthma pathogenesis. Autophagy restrains NLRP3‐induced monocyte activation in asthma models. Yet, the effects of autophagy and its master regulator, transcription factor EB (TFEB), on monocyte responses in human asthma remain unexplored. Here, we investigated whether activation of autophagy and TFEB signaling suppress inflammatory monocyte responses in asthmatic individuals.

Ligands of the transforming growth factor-β (TGF-β) superfamily, including TGF-βs, activins, and bone morphogenetic proteins (BMPs), have been implicated in hepatic development, homeostasis, and pathophysiology. We explored the mechanisms by which hepatocytes decode and integrate injury-induced signaling from TGF-βs and activins (TGF-β/Activin) and BMPs. We mapped the spatiotemporal patterns of pathway activation during liver injury induced by acetaminophen (APAP) in dual reporter mice carrying a fluorescent reporter of TGF-β/Activin signaling and a fluorescent reporter of BMP signaling. APAP intoxication induced the expression of both reporters in a zone of cells near areas of tissue damage, which showed an increase in autophagy and demarcated the borders between healthy and injured tissues. Inhibition of TGF-β superfamily signaling by overexpressing the inhibitor Smad7 exacerbated acute liver histopathology but eventually accelerated tissue recovery. Transcriptomic analysis identified autophagy as a process stimulated by TGF-β1 and BMP4 in hepatocytes, with Trp53inp2, which encodes a rate-limiting factor for autophagy initiation, as the most highly induced autophagy-related gene. Collectively, these findings illustrate the functional interconnectivity of the TGF-β superfamily signaling system, implicate the coordinated activation of TGF-β/Activin and BMP pathways in balancing tissue reparatory and regenerative processes upon APAP-induced hepatotoxicity, and highlight opportunities and potential risks associated with targeting this signaling system for treating hepatic diseases.

Transforming Growth Factor-βs (TGFβs)/Activins and Bone Morphogenetic Proteins (BMPs) have been implicated in numerous aspects of hepatic pathophysiology. However, the way by which hepatocytes integrate and decode the interplay between the TGFβ/Activin and BMP branches in health and disease is still not fully understood. To address this, TGFβ/BMP Smad- responsive double transgenic reporter mice were generated and utilized to map patterns of TGFβ- and/or BMP-pathway activation during acetaminophen- induced liver injury. TGFβ signaling was blocked either pharmacologically or by Smad7 over-expression and the transcriptomes of canonical TGFβ- and/or BMP4-treated hepatospheres and Smad7-treated livers were analyzed to highlight TGFβ-superfamily-regulated pathways and processes. Acetaminophen administration led to dynamically evolving, stage- and context-specific, patterns of hepatic TGFβ/Activin and BMP-reporter expression. TGFβ-superfamily signaling was activated in an autophagy prone zone at the borders between healthy and injured tissue. Inhibition of TGFβ-superfamily signaling attenuated autophagy, exacerbated liver histopathology, and finally led to accelerated tissue-recovery. Hallmarks of this process were the paraptosis-like cell death and the attenuation of immune and reparatory cell responses. Transcriptomic analysis highlighted autophagy as a prominent TGFβ1- and BMP4-regulated process and recognized Trp53inp2 as the top TGFβ-superfamily-regulated autophagy-related gene. Collectively, these findings implicate the coordinated activation of both canonical TGFβ-superfamily signalling branches in balancing autophagic response and tissue-reparatory and -regenerative processes upon acetaminophen-induced hepatotoxicity, highlighting opportunities and putative risks associated with their targeting for treatment of hepatic diseases. ### Competing Interest Statement The authors have declared no competing interest.

Various ligands and receptors of the transforming growth factor-β superfamily have been found upregulated following traumatic brain injury; however, the role of this signalling system in brain injury pathophysiology is not fully characterized. To address this, we utilized an acute stab wound brain injury model to demonstrate that hallmarks of transforming growth factor-β superfamily system activation, such as levels of phosphorylated Smads, ligands and target genes for both transforming growth factor-β and bone morphogenetic protein pathways, were upregulated within injured tissues. Using a bone morphogenetic protein-responsive reporter mouse model, we showed that activation of the bone morphogenetic protein signalling pathway involves primarily astrocytes that demarcate the wound area. Insights regarding the potential role of transforming growth factor-β superfamily activation in glia cells within the injured tissues were obtained indirectly by treating purified reactive astrocytes and microglia with bone morphogenetic protein-4 or transforming growth factor-β1 and characterizing changes in their transcriptional profiles. Astrocytes responded to both ligands with considerably overlapping profiles, whereas, microglia responded selectively to transforming growth factor-β1. Novel pathways, crucial for repair of tissue-injury and blood-brain barrier, such as activation of cholesterol biosynthesis and transport, production of axonal guidance and extracellular matrix components were upregulated by transforming growth factor-β1 and/or bone morphogenetic protein-4 in astrocytes. Moreover, both ligands in astrocytes and transforming growth factor-β1 in microglia shifted the phenotype of reactive glia cells towards the anti-inflammatory and tissue reparatory 'A2'-like and 'M0/M2'-like phenotypes, respectively. Increased expression of selected key components of the in vitro modulated pathways and markers of 'A2'-like astrocytes was confirmed within the wound area, suggesting that these processes could also be modulated in situ by the integrated action of transforming growth factor-β and/or bone morphogenetic protein-mediated signalling. Collectively, our study provides a comprehensive comparative analysis of transforming growth factor-β superfamily signalling in reactive astrocytes and microglia and points towards a crucial role of both transforming growth factor-β and bone morphogenetic protein pathways in modulating the inflammatory and brain injury reparatory functions of activated glia cells.

Lambda interferons (IFNλs) or type III IFNs share homology, expression patterns, signaling cascades, and antiviral functions with type I IFNs. This has complicated the unwinding of their unique non-redundant roles. Through the systematic study of influenza virus infection in mice, we herein show that IFNλs are the first IFNs produced that act at the epithelial barrier to suppress initial viral spread without activating inflammation. If infection progresses, type I IFNs come into play to enhance viral resistance and induce pro-inflammatory responses essential for confronting infection but causing immunopathology. Central to this are neutrophils which respond to both cytokines to upregulate antimicrobial functions but exhibit pro-inflammatory activation only to type I IFNs. Accordingly, Ifnlr1-/- mice display enhanced type I IFN production, neutrophilia, lung injury, and lethality, while therapeutic administration of PEG-IFNλ potently suppresses these effects. IFNλs therefore constitute the front line of antiviral defense in the lung without compromising host fitness.

Background Nitric oxide (NO) is central in the process of vasodilatation (1). Limited bioavailability of NO often associates with endothelial dysfunction, a precursor to atherogenesis (1). Such dysfunction is often observed in patients with chronic conditions such as Rheumatoid Arthritis (RA) (2) and Chronic Obstructive Pulmonary Disease (COPD) (3). Common therapies for this include the administration of nitrate-rich medication. However, in the general population beetroot juice supplementation has been shown to increase NO bioavailability (4). It could therefore have beneficial effects on endothelial function of these patients as well. Objectives To evaluate the effects of short-term beetroot juice supplementation on endothelial function in patients with RA and COPD. Methods A total of 28 patients, 9 with RA, 9 with COPD and 10 healthy controls participated in the study. Following consent, they were asked to report at the testing venue (Ultrasonography Laboratory, General Hospital of Trikala) early in the morning, following an overnight fast. Demographic and disease characteristics were recorded; height, weight, classical risk factor for cardiovascular disease and body composition were assessed. Endothelial function was assessed using flow mediated vasodilatation. They randomly received either beetroot (experimental leg) or blackcurrant juice (control leg), which they consumed daily for two weeks. Thereafter they were re-evaluated. Following a two-week washout period, they crossed over to the other leg of the study. Results There was no difference in pre-occlusion diameter between any of the time-points. Endothelial function was significantly improved following beetroot juice consumption for both patient groups (RA: 2.6% [0.9 – 6.2] vs 10.7% [6.2 – 11.7]; p=0.013. COPD: 3.4% [1.2 – 4.8] vs 7.8% [3.6 – 10.2]; p=0.034) while it remained relatively unaffected by blackcurrant consumption (Overall: 3.9% [0 – 5.1] vs 4.2% [2.3 – 6.1]; p=0.26). Conclusions A two week consumption of beetroot juice seems to be able to improve endothelial function among patients with RA and COPD. This could elicit significant health benefits. Further research to investigate the benefits of longer-term use on endothelial function and related cardiovascular health, as well as disease symptoms, and quality of life is advocated. References Moncada, S. and Higgs, E.A. The discovery of nitric oxide and its role in vascular biology. British Journal of Pharmacology 2006, 147: S193–S201. Sandoo, A. et al. Vascular function and morphology in rheumatoid arthritis: a systematic review. Rheumatology 2011, 50 (11): 2125–2139. Clarenbach, C.F. Determinants of endothelial function in patients with COPD. European Respiratory Journal 2013, 42 (5): 1194–1204. Clifford, T. et al. The Potential Benefits of Red Beetroot Supplementation in Health and Disease. Nutrients 2015, 7.4: 2801–2822. Disclosure of Interest None declared

Background: Although acute exacerbations, mostly triggered by viruses, account for the majority of hospitalizations in asthmatic patients, there is still very little known about the pathophysiologic mechanisms involved. Plasmacytoid dendritic cells (pDCs), prominent cells of antiviral immunity, exhibit proinflammatory or tolerogenic functions depending on the context, yet their involvement in asthma exacerbations remains unexplored. Objectives: We sought to investigate the role of pDCs in allergic airway inflammation and acute asthma exacerbations. Methods: Animal models of allergic airway disease (AAD) and virus-induced AAD exacerbations were used to dissect pDC function in vivo and unwind the potential mechanisms involved. Sputum from asthmatic patients with stable disease or acute exacerbations was further studied to determine the presence of pDCs and correlation with inflammation. Results: pDCs were key mediators of the immunoinflammatory cascade that drives asthma exacerbations. In animal models of AAD and rhinovirus-induced AAD exacerbations, pDCs were recruited to the lung during inflammation and migrated to the draining lymph nodes to boost T(H)2-mediated effector responses. Accordingly, pDC depletion after allergen challenge or during rhinovirus infection abrogated exacerbation of inflammation and disease. Central to this process was IL-25, which was induced by allergen challenge or rhinovirus infection and conditioned pDCs for proinflammatory function. Consistently, in asthmatic patients pDC numbers were markedly increased during exacerbations and correlated with the severity of inflammation and the risk for asthma attacks. Conclusions: Our studies uncover a previously unsuspected role of pDCs in asthma exacerbations with potential diagnostic and prognostic implications. They also propose the therapeutic targeting of pDCs and IL-25 for the treatment of acute asthma.

TGF-β signaling regulates a variety of cellular processes, including proliferation, apoptosis, differentiation, immune responses, and fibrogenesis. Here, we describe a lysine methylation-mediated mechanism that controls the pro-fibrogenic activity of TGF-β. We find that the methyltransferase Set9 potentiates TGF-β signaling by targeting Smad7, an inhibitory downstream effector. Smad7 methylation promotes interaction with the E3 ligase Arkadia and, thus, ubiquitination-dependent degradation. Depletion or pharmacological inhibition of Set9 results in elevated Smad7 protein levels and inhibits TGF-β-dependent expression of genes encoding extracellular matrix components. The inhibitory effect of Set9 on TGF-β-mediated extracellular matrix production is further demonstrated in mouse models of pulmonary fibrosis. Lung fibrosis induced by bleomycin or Ad-TGF-β treatment was highly compromised in Set9-deficient mice. These results uncover a complex regulatory interplay among multiple Smad7 modifications and highlight the possibility that protein methyltransferases may represent promising therapeutic targets for treating lung fibrosis.

Introduction: Pulmonary involvement leading to interstitial lung disease (ILD) is the most common and potentially most devastating complication of Rheumatoid Arthritis (RA). The lifetime risk of ILD development in RA patients is approximately 10%. Still, there is very little known about the presence of pro-inflammatory and pro-fibrotic mediators and their potential involvement to disease pathophysiology. Aim: The primary objective of this study was to assess the expression of various inflammatory mediators in bronchoalveolar lavage of RA-ILD patients and compare it with that of ILD and no-ILD RA patients. The secondary objective was to assess the presence of key leads in the SKG mouse model of RA and ILD in order to study the functional relevance in disease development and progression. Methods: A total number of 15 patients were recruited to the study and divided into 3 groups 1)RA with ILD, 2)RA without ILD and 3)Idiopathic pulmonary fibrosis. Bronchoalveolar lavage fluid was obtained and analysed by Luminex and Elisa. SKG mice were also used and BAL was investigated. Results: Various inflammatory mediators including Activin A, VEGF, IL-8, MCP-1, MIP-1a and MIP-1b were found to be up-regulated in the BAL from patients with ILD-RA. Activin-A, a cytokine with both inflammatory and pro-fibrotic activity, was also abundant in BAL from SKG mice with lung fibrosis. Conclusions: Our results reveal that multiple pro-inflammatory and pro-fibrotic mediators are present in RA-ILD and raise the possibility that Activin A may also be important in the disease process.

During the 26 years that have elapsed since its discovery, activin-A, a member of the transforming growth factor β super-family originally discovered from its capacity to stimulate follicle-stimulating hormone production by cultured pituitary gonadotropes, has been established as a key regulator of various fundamental biological processes, such as development, homeostasis, inflammation, and tissue remodeling. Deregulated expression of activin-A has been observed in several human diseases characterized by an immuno-inflammatory and/or tissue remodeling component in their pathophysiology. Various cell types have been recognized as sources of activin-A, and plentiful, occasionally contradicting, functions have been described mainly by in vitro studies. Not surprisingly, both harmful and protective roles have been postulated for activin-A in the context of several disorders. Recent findings have further expanded the functional repertoire of this molecule demonstrating that its ectopic overexpression in mouse airways can cause pathology that simulates faithfully human acute respiratory distress syndrome, a disorder characterized by strong involvement of neutrophils. This finding when considered together with the recent discovery that neutrophils constitute an important source of activin-A in vivo and earlier observations of upregulated activin-A expression in diseases characterized by strong activation of neutrophils may collectively imply a more intimate link between activin-A expression and neutrophil reactivity. In this review, we provide an outline of the functional repertoire of activin-A and suggest that this growth factor functions as a guardian of homeostasis, a modulator of immunity and an orchestrator of tissue repair activities. In this context, a relationship between activin-A and neutrophils may be anything but coincidental.

Πλήθος μελετών με τη χρήση γενετικά τροποποιημένων ζωικών μοντέλων έχει αναδείξει τη σημασία της υπερ-οικογένειας του παράγοντα TGF-β στην ανάπτυξη, την ομοιόσταση και την παθοφυσιολογία του οργανισμού, κατ’ αντιστοιχία με μελέτες που καταδεικνύουν το φυσιολογικό και παθολογικό ρόλο της υπερ-οικογένειας του TGF-β στον άνθρωπο. Παρόλα αυτά, ο ακριβής μηχανισμός δράσης, οι κυτταρικοί στόχοι, το γονιδιακό πρότυπο έκφρασης και το χωροχρονικό πρότυπο κατανομής των κυττάρων-δεκτών της σηματοδότησης από τους BMPs ή τους TGF-β/Ακτιβίνες, δεν έχουν διαλευκανθεί ακόμα. Για να προσεγγίσουμε αυτά τα ερωτήματα, δημιουργήσαμε και αναλύσαμε δυο διαγονιδιακές σειρές μυών αναφοράς, μια που εκφράζει την πρωτεΐνη eGFP υπό τον έλεγχο ενός BMP-αποκρινόμενου υποκινητή (BRE-eGFP διαγονιδιακή σειρά) για την ανίχνευση των κυτταρικών στόχων του κανονικού BMP-μονοπατιού και μια νέα διαγονιδιακή σειρά, που εκφράζει την πρωτεΐνη mRFP κάτω από τον έλεγχο ενός TGF-β/Activin-αποκρινόμενου υποκινητή (TRE-mRFP διαγονιδιακή σειρά). Συνδυάζοντας αυτές τις σειρές, η ανάλυση των διπλά διαγονιδιακών μυών αναφοράς επέτρεψε τη συνεχή και ταυτόχρονη παρακολούθηση και των δύο σηματοδοτικών μονοπατιών.Ανάλυση διαφόρων οργάνων αποκάλυψε τους κυτταρικούς στόχους της σηματοδότησης από την υπεροικογένεια του TGF-β, ενώ ταυτόχρονα επιβεβαιώθηκε η ενεργοποίηση των σηματοδοτικών αυτών μονοπατιών σε καταστάσεις φλεγμονής και ιστικής βλάβης, αναδεικνύοντας τη σημασία αυτών των μορίων, όχι μόνο στην ομοιόσταση αλλά και σε παθολογικές καταστάσεις.Τέλος, κατέστη δυνατή η απομόνωση των κυτταρικών στόχων του BMP- και TGF-β/Activin-μονοπατιού στο ενήλικο ήπαρ και η εν τω βάθη ανάλυση του γονιδιακού προτύπου έκφρασης αυτών των κυτταρικών πληθυσμών, επιτρέποντας έτσι για πρώτη φορά τη διερεύνηση νέων γονιδίων-στόχων της TGF-β υπερ-οικογένειας.Η μελέτη αυτή ανέδειξε την πολυπλοκότητα και δυναμικότητα της ενεργοποίησης του TGF-β σηματοδοτικού μονοπατιού κατά την ανάπτυξη, την ομοιόσταση και την ιστική αναδόμηση και ανέπτυξε μοναδικά εργαλεία που επιτρέπουν την απομόνωση των κυττάρων που βρίσκονται κάτω από τη δράση αυτού του σηματοδοτικού μονοπατιού.

Rationale: Activin-A is up-regulated in various respiratory disorders. However, its precise role in pulmonary pathophysiology has not been adequately substantiated in vivo.Objectives: To investigate in vivo the consequences of dysregulated Activin-A expression in the lung and identify key Activin-A-induced processes that contribute to respiratory pathology.Methods: Activin-A was ectopically expressed in murine lung, and functional, structural, and molecular alterations were extensively analyzed. The validity of Activin-A as a therapeutic target was demonstrated in animals overexpressing Activin-A or treated with intratracheal instillation of LPS. Relevancy to human pathology was substantiated by demonstrating high Activin-A levels in bronchoalveolar lavage (BAL) samples from patients with acute respiratory distress syndrome (ARDS).Measurements and Main Results: Overexpression of Activin-A in mouse airways caused pulmonary pathology reminiscent of acute lung injury (ALI)/ARDS. Activin-A triggered a lasting inflammatory response characterized by acute alveolar cell death and hyaline membrane formation, sustained up-regulation of high-mobility group box 1, development of systemic hypercoagulant state, reduction of surfactant proteins SpC, SpB, and SpA, decline of lung compliance, transient fibrosis, and eventually emphysema. Therapeutic neutralization of Activin-A attenuated the ALI/ARDS-like pathology induced either by ectopic expression of Activin-A or by intratracheal instillation of LPS. In line with the similarity of the Activin-A-induced phenotype to human ARDS, selective up-regulation of Activin-A was found in BAL of patients with ARDS.Conclusions: Our studies demonstrate for the first time in vivo the pathogenic consequences of deregulated Activin-A expression in the lung, document novel aspects of Activin-A biology that provide mechanistic explanation for the observed phenotype, link Activin-A to ALI/ARDS pathophysiology, and provide the rationale for therapeutic targeting of Activin-A in these disorders.

Signaling by Bone Morphogenetic Proteins (BMP) has been implicated in early lung development, adult lung homeostasis and tissue-injury repair. However, the precise mechanism of action and the spatio-temporal pattern of BMP-signaling during these processes remains inadequately described. To address this, we have utilized a transgenic line harboring a BMP-responsive eGFP-reporter allele (BRE-eGFP) to construct the first detailed spatiotemporal map of canonical BMP-pathway activation during lung development, homeostasis and adult-lung injury repair. We demonstrate that during the pseudoglandular stage, when branching morphogenesis progresses in the developing lung, canonical BMP-pathway is active mainly in the vascular network and the sub-epithelial smooth muscle layer of the proximal airways. Activation of the BMP-pathway becomes evident in epithelial compartments only after embryonic day (E) 14.5 primarily in cells negative for epithelial-lineage markers, located in the proximal portion of the airway-tree, clusters adjacent to neuro-epithelial-bodies (NEBs) and in a substantial portion of alveolar epithelial cells. The pathway becomes activated in isolated E12.5 mesenchyme-free distal epithelial buds cultured in Matrigel suggesting that absence of reporter activity in these regions stems from a dynamic cross-talk between endoderm and mesenchyme. Epithelial cells with activated BMP-pathway are enriched in progenitors capable of forming colonies in three-dimensional Matrigel cultures. As lung morphogenesis approaches completion, eGFP-expression declines and in adult lung its expression is barely detectable. However, upon tissue-injury, either with naphthalene or bleomycin, the canonical BMP-pathways is re-activated, in bronchial or alveolar epithelial cells respectively, in a manner reminiscent to early lung development and in tissue areas where reparatory progenitor cells reside. Our studies illustrate the dynamic activation of canonical BMP-pathway during lung development and adult lung tissue-repair and highlight its involvement in two important processes, namely, the early development of the pulmonary vasculature and the management of epithelial progenitor pools both during lung development and repair of adult lung tissue-injury.

IL‐28 (IFN‐λ) cytokines exhibit potent antiviral and antitumor function but their full spectrum of activities remains largely unknown. Recently, IL‐28 cytokine family members were found to be profoundly down‐regulated in allergic asthma. We now reveal a novel role of IL‐28 cytokines in inducing type 1 immunity and protection from allergic airway disease. Treatment of wild‐type mice with recombinant or adenovirally expressed IL‐28A ameliorated allergic airway disease, suppressed Th2 and Th17 responses and induced IFN‐γ. Moreover, abrogation of endogenous IL‐28 cytokine function in IL‐28Rα −/− mice exacerbated allergic airway inflammation by augmenting Th2 and Th17 responses, and IgE levels. Central to IL‐28A immunoregulatory activity was its capacity to modulate lung CD11c + dendritic cell (DC) function to down‐regulate OX40L, up‐regulate IL‐12p70 and promote Th1 differentiation. Consistently, IL‐28A‐mediated protection was absent in IFN‐γ −/− mice or after IL‐12 neutralization and could be adoptively transferred by IL‐28A‐treated CD11c + cells. These data demonstrate a critical role of IL‐28 cytokines in controlling T cell responses in vivo through the modulation of lung CD11c + DC function in experimental allergic asthma. →See accompanying Closeup by Michael R Edwards and Sebastian L Johnston http://dx.doi.org/10.1002/emmm.201100143

RATIONALE:Toll-like receptor (TLR) 7/8 ligands are promising candidate drugs for the treatment of allergic asthma and rhinitis. Although their clinical application depends on the development of strategies for topical administration to the lung, this has not been explored in preclinical disease models.OBJECTIVES:To examine the therapeutic effectiveness, persistence of effect, and mode of action of intranasal TLR7 ligand administration in allergic airway disease.METHODS:Wild-type, IFN-alpha receptor (IFN-alphaR)(-/-), IFN-gamma(-/-), CD8(-/-), TLR7(-/-), and radiation-induced chimeric mice deficient in hematopoietic TLR7 expression were subjected to an established model of allergic airway disease. R-848, a specific TLR7 agonist in mice, was administered prophylactically or therapeutically and effects of treatment on helper T-cell type 2 (Th2) responses, eosinophilia, goblet cell metaplasia, and airway hyperresponsiveness were assessed.MEASUREMENTS AND MAIN RESULTS:Intranasal R-848 administration induced a transient immune response characterized by type I interferon production and infiltration of innate immune cells into the lung. This conferred long-term suppression of allergic airway disease via two complementary molecular processes, one mediated by type I interferons and providing acute protection by directly inhibiting effector Th2 responses, and one mediated by immunoregulatory CD8(+) T cells and inducing long-lasting protection by suppressing Th2 responses in an IFN-gamma-dependent manner.CONCLUSIONS:Intranasal R-848 administration is an effective treatment for allergic airway disease. It hijacks an otherwise proinflammatory immune process triggered by TLR7 to mediate long-lasting disease suppression. This provides important insight into the efficacy and mode of action of TLR7 ligands in murine models of allergic airway disease and paves the way for their clinical application in humans.