Crosstalk between TGF-β1 and complement activation augments epithelial injury in pulmonary fibrosis

Elongation factor-2 kinase acts downstream of p38 MAPK to regulate proliferation, apoptosis and autophagy in human lung fibroblasts

Idiopathic pulmonary fibrosis (IPF) is a chronic, fatal and progressive fibro-proliferative lung disease, and fibroblast-to-myofibroblast differentiation is a crucial process in the development of IPF. Elongation factor-2 kinase (eEF2K) has been reported to play an important role in various disease types, but the role of eEF2K in IPF is unknown. In this study, we investigated the role of eEF2K in normal lung fibroblast (NHLF) proliferation, differentiation, apoptosis, and autophagy as well as the interaction between eEF2K and p38 MAPK signaling through in vitro experiments. We found that the inhibition of eEF2K markedly augmented cell proliferation and differentiation, suppressed apoptosis and autophagy, and reversed the anti-fibrotic effects of a p38 MAPK inhibitor. Together, our results indicate that eEF2K might inhibit TGF-β1-induced NHLF proliferation and differentiation and activate NHLF cell apoptosis and autophagy through p38 MAPK signaling, which might ameliorate lung fibroblast-to-myofibroblast differentiation.

Upregulated miR-29c suppresses silica-induced lung fibrosis through the Wnt/β-catenin pathway in mice

Silicosis is an irreversible lung disease resulting from long-term inhalation of occupational dust containing silicon dioxide. However, the pathogenesis of silicosis has not been clearly understood yet. Accumulating evidence suggests that miR-29 may have a significant anti-fibrotic capacity, meanwhile it may relate to Wnt/β-catenin pathway. The purpose of this study was to discuss the role of miR-29 in the progression of silicosis. A lentiviral vector was constructed, named Lv-miR-29c, which was overexpressing miR-29c. In vivo, intratracheal treatment with Lv-miR-29c significantly increased expression of miR-29c, and reduced expression of β-catenin, matrix metalloproteinase (MMP)-2, and MMP-9 in the lung and levels of transforming growth factor-beta 1 (TGF-β1) and interleukin-6 (IL-6) in bronchoalveolar lavage fluid, and notably attenuated pulmonary fibrosis as evidenced by hydroxyproline content in silica-administered mice. These results indicated that miR-29c inhibited the development of silica-induced lung fibrosis. Thus, miR-29c may be a candidate target for silicosis treatment via its regulation of the Wnt/β-catenin pathway.

A novel multiplex detection array revealed systemic complement activation in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is one of the most common tumors within the oral cavity. Early diagnosis and prognosis tools are urgently needed. This study aimed to investigate the activation of the complement system in OSCC patients as potential biomarker. Therefore, an innovative complement activation array was developed. Characterized antibodies detecting the complement activation specific epitopes C3a, C5a and sC5b-9 along with control antibodies were implemented into a suspension bead array. Human serum from a healthy (n = 46) and OSCC patient (n = 57) cohort were used to investigate the role of complement activation in oral tumor progression. The novel multiplex assay detected C3a, C5a and sC5b-9 from a minimal sample volume of human tears, aqueous humor and blood samples. Limits of detection were 0.04 ng/mL for C3a, 0.03 ng/mL for C5a and 18.9 ng/mL for sC5b-9, respectively. Biological cut-off levels guaranteed specific detections from serum. The mean serum concentration of a healthy control cohort was 680 ng/mL C3a, 70 ng/mL C5a and 2247 ng/mL sC5b-9, respectively. The assay showed an intra-assay precision of 2.9-6.4% and an inter-assay precision of 9.2-18.2%. Increased systemic C5a (p < 0.0001) and sC5b-9 (p = 0.01) concentrations in OSCC patients were determined using the validated multiplex complement assay. Higher C5a concentrations correlated with tumor differentiation and OSCC extension state. Systemic sC5b-9 determination provided a novel biomarker for infiltrating tumor growth and C3a levels were associated with local tumor spreading. Our study suggests that systemic complement activation levels in OSCC patients may be useful to assess disease progression.

Potential Mechanisms Underlying TGF-β-mediated Complement Activation in Lung Fibrosis

While our previous studies suggest that limiting bleomycin-induced complement activation suppresses TGF-β signaling, the specific hierarchical interactions between TGF-β and complement in lung fibrosis are unclear. Herein, we investigated the mechanisms underlying TGF-β-induced complement activation in the pathogenesis of lung fibrosis. C57-BL6 mice were given intratracheal instillations of adenoviral vectors overexpressing TGF-β (Ad-TGFβ) or the firefly gene-luciferase (Ad-Luc; control). Two weeks later, mice with fibrotic lungs were instilled RNAi specific to receptors for C3a or C5a-C3ar or C5ar, and sacrificed at day 28. Histopathological analyses revealed that genetic silencing of C3ar or C5ar arrested the progression of TGF-β-induced lung fibrosis, collagen deposition and content (hydroxyproline, col1a1/2); and significantly suppressed local complement activation. With genetic silencing of either C3ar or C5ar, in Ad-TGFβ-injured lungs: we detected the recovery of Smad7 (TGF-β inhibitor) and diminished local release of DAF (membrane-bound complement inhibitor); in vitro: TGF-β-mediated loss of DAF was prevented. Conversely, blockade of the TGF-β receptor prevented C3a-mediated loss of DAF in both normal primary human alveolar and small airway epithelial cells. Of the 52 miRNAs analyzed as part of the Affymetrix array, normal primary human SAECs exposed to C3a, C5a or TGF-β caused discrete and overlapping miRNA regulation related to epithelial proliferation or apoptosis (miR-891A, miR-4442, miR-548, miR-4633), cellular contractility (miR-1197) and lung fibrosis (miR-21, miR-200C, miR-31HG, miR-503). Our studies present potential mechanisms by which TGF-β activates complement and promotes lung fibrosis.

IL-17A deficiency mitigates bleomycin-induced complement activation during lung fibrosis

Interleukin 17A (IL-17A) and complement (C') activation have each been implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF). We have reported that IL-17A induces epithelial injury via TGF-β in murine bronchiolitis obliterans; that TGF-β and the C' cascade present signaling interactions in mediating epithelial injury; and that the blockade of C' receptors mitigates lung fibrosis. In the present study, we investigated the role of IL-17A in regulating C' in lung fibrosis. Microarray analyses of mRNA isolated from primary normal human small airway epithelial cells indicated that IL-17A (100 ng/ml; 24 h; n = 5 donor lungs) induces C' components (C' factor B, C3, and GPCR kinase isoform 5), cytokines (IL8, -6, and -1B), and cytokine ligands (CXCL1, -2, -3, -5, -6, and -16). IL-17A induces protein and mRNA regulation of C' components and the synthesis of active C' 3a (C3a) in normal primary human alveolar type II epithelial cells (AECs). Wild-type mice subjected to IL-17A neutralization and IL-17A knockout (il17a^-/- ) mice were protected against bleomycin (BLEO)-induced fibrosis and collagen deposition. Further, BLEO-injured il17a^-/- mice had diminished levels of circulating Krebs Von Den Lungen 6 (alveolar epithelial injury marker), local caspase-3/7, and local endoplasmic reticular stress-related genes. BLEO-induced local C' activation [C3a, C5a, and terminal C' complex (C5b-9)] was attenuated in il17a^-/- mice, and IL-17A neutralization prevented the loss of epithelial C' inhibitors (C' receptor-1 related isoform Y and decay accelerating factor), and an increase in local TUNEL levels. RNAi-mediated gene silencing of il17a in fibrotic mice arrested the progression of lung fibrosis, attenuated cellular apoptosis (caspase-3/7) and lung deposition of collagen and C' (C5b-9). Compared to normals, plasma from IPF patients showed significantly higher hemolytic activity. Our findings demonstrate that limiting complement activation by neutralizing IL-17A is a potential mechanism in ameliorating lung fibrosis.-Cipolla, E., Fisher, A. J., Gu, H., Mickler, E. A., Agarwal, M., Wilke, C. A., Kim, K. K., Moore, B. B., Vittal, R. IL-17A deficiency mitigates bleomycin-induced complement activation during lung fibrosis.

Hypoxia-Inducible Factor-1α Regulates CD55 in Airway Epithelium

Airway epithelial CD55 down-regulation occurs in several hypoxia-associated pulmonary diseases, but the mechanism is unknown. Using in vivo and in vitro assays of pharmacologic inhibition and gene silencing, the current study investigated the role of hypoxia-inducible factor (HIF)-1α in regulating airway epithelial CD55 expression. Hypoxia down-regulated CD55 expression on small-airway epithelial cells in vitro, and in murine lungs in vivo; the latter was associated with local complement activation. Treatment with pharmacologic inhibition or silencing of HIF-1α during hypoxia-recovered CD55 expression in small-airway epithelial cells. HIF-1α overexpression or blockade, in vitro or in vivo, down-regulated CD55 expression. Collectively, these data show a key role for HIF-1α in regulating the expression of CD55 on airway epithelium.

The peripheral blood proteome signature of idiopathic pulmonary fibrosis is distinct from normal and is associated with novel immunological processes

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal interstitial pneumonia. The disease pathophysiology is poorly understood and the etiology remains unclear. Recent advances have generated new therapies and improved knowledge of the natural history of IPF. These gains have been brokered by advances in technology and improved insight into the role of various genes in mediating disease, but gene expression and protein levels do not always correlate. Thus, in this paper we apply a novel large scale high throughput aptamer approach to identify more than 1100 proteins in the peripheral blood of well-characterized IPF patients and normal volunteers. We use systems biology approaches to identify a unique IPF proteome signature and give insight into biological processes driving IPF. We found IPF plasma to be altered and enriched for proteins involved in defense response, wound healing and protein phosphorylation when compared to normal human plasma. Analysis also revealed a minimal protein signature that differentiated IPF patients from normal controls, which may allow for accurate diagnosis of IPF based on easily-accessible peripheral blood. This report introduces large scale unbiased protein discovery analysis to IPF and describes distinct biological processes that further inform disease biology.

Inhibition of Complement Retards Ankylosing Spondylitis Progression

Ankylosing spondylitis (AS) is a chronic axial spondyloarthritis (SpA) resulting in back pain and progressive spinal ankyloses. Currently, there are no effective therapeutics targeting AS largely due to elusive pathogenesis mechanisms, even as potential candidates such as HLA-B27 autoantigen have been identified. Herein, we employed a proteoglycan (PG)-induced AS mouse model together with clinical specimens, and found that the complement system was substantially activated in the spinal bone marrow, accompanied by a remarkable proportion alteration of neutrophils and macrophage in bone marrow and spleen, and by the significant increase of TGF-β1 in serum. The combined treatment with a bacteria-derived complement inhibitor Efb-C (C-terminal of extracellular fibrinogen-binding protein of Staphylococcus aureus) remarkably retarded the progression of mouse AS by reducing osteoblast differentiation. Furthermore, we demonstrated that two important modulators involved in AS disease, TGF-β1 and RANKL, were elevated upon in vitro complement attack in osteoblast and/or osteoclast cells. These findings further unravel that complement activation is closely related with the pathogenesis of AS, and suggest that complement inhibition may hold great potential for AS therapy.

Anti-fibrotic effects of valproic acid: role of HDAC inhibition and associated mechanisms

Tissue injuries and pathological insults produce oxidative stress, genetic and epigenetic alterations, which lead to an imbalance between pro- and anti-fibrotic molecules, and subsequent accumulation of extracellular matrix, thereby fibrosis. Various molecular pathways play a critical role in fibroblasts activation, which promotes the extracellular matrix production and accumulation. Recent reports highlighted that histone deacetylases (HDACs) are upregulated in various fibrotic disorders and play a central role in fibrosis, while HDAC inhibitors exert antifibrotic effects. Valproic acid is a first-line anti-epileptic drug and a proven HDAC inhibitor. This review provides the current research and novel insights on antifibrotic effects of valproic acid in various fibrotic conditions with an emphasis on the possible strategies for treatment of fibrosis.

Suramin inhibits antibody binding to cell surface antigens and disrupts complement-mediated mesangial cell lysis

Suramin inhibits immune responses and protects cells against inflammatory cell injury. However, little is known about its mechanisms. Using an in vitro model of glomerular mesangial cell (MC) lysis induced by antibodies plus complement, we investigated the potential protective effects and mechanisms of suramin on immunologic cell injury. Exposure of rat MCs to anti-Thy-1 antibody plus complement or anti-MC rabbit serum caused complement-dependent cell lysis, which was blocked by suramin and its structural analogue NF023 and NF049, but not by PPADS, an antagonist of purinergic receptors. Addition of exogenous ATP also failed to affect MC lysis. Further analysis revealed that suramin interfered with antibody binding to cell membrane antigens and suppressed antibody-induced phosphorylation of several proteins, including p38. Inhibition of p38 with chemical inhibitor significantly attenuated cell injury. Collectively, our results indicate that suramin protects cells against antibody-initiated and complement-dependent cell injury through inhibition of antibody binding to cell surface antigens and suppression of p38 activation. Our study thus provides novel mechanistic insights into the actions of suramin and suggests that suramin might be used to treat certain immune diseases.

Contribution of the anaphylatoxin receptors, C3aR and C5aR, to the pathogenesis of pulmonary fibrosis

Complement activation, an integral arm of innate immunity, may be the critical link to the pathogenesis of idiopathic pulmonary fibrosis (IPF). Whereas we have previously reported elevated anaphylatoxins-complement component 3a (C3a) and complement component 5a (C5a)-in IPF, which interact with TGF-β and augment epithelial injury in vitro, their role in IPF pathogenesis remains unclear. The objective of the current study is to determine the mechanistic role of the binding of C3a/C5a to their respective receptors (C3aR and C5aR) in the progression of lung fibrosis. In normal primary human fetal lung fibroblasts, C3a and C5a induces mesenchymal activation, matrix synthesis, and the expression of their respective receptors. We investigated the role of C3aR and C5aR in lung fibrosis by using bleomycin-injured mice with fibrotic lungs, elevated local C3a and C5a, and overexpression of their receptors via pharmacologic and RNA interference interventions. Histopathologic examination revealed an arrest in disease progression and attenuated lung collagen deposition (Masson's trichrome, hydroxyproline, collagen type I α 1 chain, and collagen type I α 2 chain). Pharmacologic or RNA interference-specific interventions suppressed complement activation (C3a and C5a) and soluble terminal complement complex formation (C5b-9) locally and active TGF-β1 systemically. C3aR/C5aR antagonists suppressed local mRNA expressions of tgfb2, tgfbr1/2, ltbp1/2, serpine1, tsp1, bmp1/4, pdgfbb, igf1, but restored the proteoglycan, dcn Clinically, compared with pathologically normal human subjects, patients with IPF presented local induction of C5aR, local and systemic induction of soluble C5b-9, and amplified expression of C3aR/C5aR in lesions. The blockade of C3aR and C5aR arrested the progression of fibrosis by attenuating local complement activation and TGF-β/bone morphologic protein signaling as well as restoring decorin, which suggests a promising therapeutic strategy for patients with IPF.-Gu, H., Fisher, A. J., Mickler, E. A., Duerson, F., III, Cummings, O. W., Peters-Golden, M., Twigg, H. L., III, Woodruff, T. M., Wilkes, D. S., Vittal, R. Contribution of the anaphylatoxin receptors, C3aR and C5aR, to the pathogenesis of pulmonary fibrosis.

Blocking the Wnt/β-Catenin Pathway by Lentivirus-Mediated Short Hairpin RNA Targeting β-Catenin Gene Suppresses Silica-Induced Lung Fibrosis in Mice

Silicosis is a form of occupational lung disease caused by inhalation of crystalline silica dust. While the pathogenesis of silicosis is not clearly understood, the Wnt/β-catenin signaling pathway is thought to play a major role in lung fibrosis. To explore the role of Wnt/β-catenin pathway in silicosis, we blocked Wnt/β-catenin pathway both in silica-treated MLE-12 cells (a mouse pulmonary epithelial cell line) and in a mouse silicosis model by using a lentiviral vector expressing a short hairpin RNA silencing β-catenin (Lv-shβ-catenin). In vitro, Lv-shβ-catenin significantly decreased the expression of β-catenin, MMP2 and MMP9, and secretion of TGF-β1. In vivo, intratracheal treatment with Lv-shβ-catenin significantly reduced expression of β-catenin in the lung and levels of TGF-β1 in bronchoalveolar lavage fluid, and notably attenuated pulmonary fibrosis as evidenced by hydroxyproline content and collagen I\III synthesis in silica-administered mice. These results indicate that blockade of the Wnt/β-catenin pathway can prevent the development of silica-induced lung fibrosis. Thus Wnt/β-catenin pathway may be a target in prevention and treatment of silicosis.

Affect of Early Life Oxygen Exposure on Proper Lung Development and Response to Respiratory Viral Infections

Children born preterm often exhibit reduced lung function and increased severity of response to respiratory viruses, suggesting that premature birth has compromised proper development of the respiratory epithelium and innate immune defenses. Increasing evidence suggests that premature birth promotes aberrant lung development likely due to the neonatal oxygen transition occurring before pulmonary development has matured. Given that preterm infants are born at a point of time where their immune system is also still developing, early life oxygen exposure may also be disrupting proper development of innate immunity. Here, we review current literature in hopes of stimulating research that enhances understanding of how the oxygen environment at birth influences lung development and host defense. This knowledge may help identify those children at risk for disease and ideally culminate in the development of novel therapies that improve their health.