Obliterative bronchiolitis (OB) is the key impediment to the long-term survival of lung transplant recipients and the lack of a robust preclinical model precludes examining OB immunopathogenesis. In the current study, lungs from C57BL/10 H-2 b mice that are MHC compatible, but minor histocompatability antigen incompatible, were transplanted into C57BL/6 mice. Histological features and cytokine profiles of OB were assessed. Moderate rejection (grade A3) developed by day 14, with evidence of OB at that time point. At 21 days, OB was present in 55% of grafts and moderate to severe rejection (grade A3-A4) was present in all mice. At 28 days, OB was present in 44% of mice and severe rejection (grade A4) was present in all. IL-17A, but not IL-17F, splenic mRNA transcripts and serum protein levels were increased only in mice that developed OB, whereas IL-10 transcripts and protein were increased only in non-OB mice. Neutralizing IL-17 prevented OB, down regulated acute rejection, and upregulated systemic IL-10. Collectively, these data show that transplantation of minor histoincompatible lungs from C57BL/10 mice into C57BL/6 mice results in a highly reproducible preclinical model of OB. In addition, these data indicate that neutralizing IL-17A or augmenting IL-10 could be therapeutic interventions to prevent OB.

Pulmonary arterial hypertension (PAH) is characterized by increased pulmonary artery pressure and vascular resistance, typically leading to right heart failure and death. Current therapies improve quality of life of the patients but have a modest effect on long-term survival. A detailed transcriptomics and systems biology view of the PAH lung is expected to provide new testable hypotheses for exploring novel treatments. We completed transcriptomics analysis of PAH and control lung tissue to develop disease-specific and clinical data/tissue pathology gene expression classifiers from expression datasets. Gene expression data were integrated into pathway analyses. Gene expression microarray data were collected from 58 PAH and 25 control lung tissues. The strength of the dataset and its derived disease classifier was validated using multiple approaches. Pathways and upstream regulators analyses was completed with standard and novel graphical approaches. The PAH lung dataset identified expression patterns specific to PAH subtypes, clinical parameters, and lung pathology variables. Pathway analyses indicate the important global role of TNF and transforming growth factor signaling pathways. In addition, novel upstream regulators and insight into the cellular and innate immune responses driving PAH were identified. Finally, WNT-signaling pathways may be a major determinant underlying the observed sex differences in PAH. This study provides a transcriptional framework for the PAH-diseased lung, supported by previously reported findings, and will be a valuable resource to the PAH research community. Our investigation revealed novel potential targets and pathways amenable to further study in a variety of experimental systems.

Primary graft dysfunction (PGD) is a major complication following lung transplantation. We reported that anti-type V collagen (col(V)) T cell immunity was strongly associated with PGD. However, the role of preformed anti-col(V) Abs and their potential target in PGD are unknown. Col(V) immune serum, purified IgG or B cells from col(V) immune rats were transferred to WKY rat lung isograft recipients followed by assessments of lung pathology, cytokines, and PaO2/FiO2, an index of lung dysfunction in PGD. Immune serum, purified IgG, and B cells all induced pathology consistent with PGD within 4 days posttransfer; up-regulated IFN-γ, TNF-α, and IL-1β locally; and induced significant reductions in PaO2/FiO2. Depleting anti-col(V) Abs before transfer demonstrated that IgG2c was a major subtype mediating injury. Confocal microscopy revealed strong apical col(V) expression on lung epithelial, but not endothelial cells; which was consistent with the ability of col(V) immune serum to induce complement-dependent cytotoxicity only in the epithelial cells. Examination of plasma from patients with or without PGD revealed that higher levels of preformed anti-col(V) Abs were strongly associated with PGD development. This study demonstrates a major role for anti-col(V) humoral immunity in PGD, and identifies the airway epithelium as a target in PGD.

Objective. To investigate the inhibition of matrix metalloproteinase 1 (MMP-1), MMP-8, and MMP-13 by doxycycline, and to determine whether the variable hemopexin-like domain of each MMP was responsible for the differences in susceptibility to doxycycline inhibition among these collagenases.Methods. Recombinant human MMP-1 (collagenase 1), MMP-8 (collagenase 2), and MMP-13 (collagenase 3), truncated forms of MMP-8 and MMP-13 lacking the hemopexin-like domain, and a mutant form of truncated MMP-13 were used in these studies. The activity of the full-length MMP in the presence of doxycycline was tested against type II collagen, a natural substrate for the enzymes. A small peptolide substrate was used to determine which structural features of the MMPs were related to sensitivity to doxycycline inhibition.Results The matrix metalloproteinases (MMPs) represent a family of structurally related enzyme proteins that share many structural and functional characteristics (1,2), but differ in substrate specificity and cellular origin. Each of the known MMPs has at least 3 structural domains: the propeptide domain, the catalytic domain, and the hemopexin-like domain. A proline-rich hinge region of variable length is present between the catalytic domain and the hemopexin-like domain. The catalytic domain and the propeptide domain are highly conserved, while the hemopexin-like domain shows significant variability. In the gelatinases, an additional gelatinbinding domain is inserted into the catalytic domain.Three collagenases share the unique ability to cleave the triple helical region of interstitial collagens. MMP-1 (collagenase 1) has been purified from fibroblasts of humans and other animals and is expressed by a variety of connective tissues and epithelia. MMP-8 (collagenase 2) was initially purified from neutrophils, but is also expressed in cartilage (3,4). MMP-13 (collagenase 3) was originally described as rat uterine collagenase (5), but has now been shown to also be produced by human breast carcinomas and to be a major product

erative bronchiolitis (OB), a fibrotic airway lesion, is the leading cause of death after lung transplantation. Type V collagen [col(V)] overexpression and IL-17-mediated anti-col(V) immunity are key contributors to OB pathogenesis. Here, we report a previously undefined role of IL-17 in inducing col(V) overexpression, leading to epithelial mesenchymal transition (EMT) and subsequent OB. We observed IL-17-mediated induction of col(V) ␣1 chains [␣1 (V)] in normal airway epithelial cells in vitro and detected ␣1 (V)-specific antibodies in bronchoalveolar lavage fluid of lung transplant patients. Overexpression of IL-17 and col(V) was detected in OB lesions in patient lung biopsies and in a murine OB model. IL-17 is shown to induce EMT, TGF-␤ mRNA expression, and SMAD3 activation, whereas downregulating SMAD7 expression in vitro. Pharmacological inhibition of TGF-␤RI tyrosine kinase, p38 MAPK, or focal adhesion kinase prevented col(V) overexpression and EMT. In murine orthotopic lung transplants, neutralizing IL-17 significantly decreased TGF-␤ mRNA and protein expression and prevented epithelial repair/ OB. Our findings highlight a feed-forward loop between IL-17 and TGF-␤, leading to induction of col(V) and associated epithelial repair, thus providing one possible link between autoimmunity and OB after lung transplantation. autoimmunity; p38 MAPK; focal adhesion kinase; small-airway epithelial cells; RLE-6TN; mouse transplant model; epithelial-mesenchymal transition OBLITERATIVE BRONCHIOLITIS (OB) is characterized by extensive peribronchiolar fibrosis with plugs of granulation tissues (fibroblasts and collagen) that occlude small airways. OB is the key reason that the 5-yr survival of lung transplant recipients is only 50%, the worst of all major solid organ transplants (42,48).Aberrant epithelial repair is a key event in the transplanted lung (1, 9) in which bronchioles lose resident epithelial cells and become occluded by granulation tissue. Abnormal epithelial repair eventually causes an epithelial-to-mesenchymal transition (EMT), a functional and phenotypic change of epithelial cells into spindle-shaped, migratory (43) and matrix-component-secreting mesenchymal cells (10, 41), and a process associated with lung fibrosis (15,27). However, the direct connection between EMT and the in vivo phenomena of fibrosis and fibro-obliterative disease remains controversial.We and others previously reported that OB is associated with dysregulation of two types of collagen: 1) marked increase in type V collagen [col(V)], a quantitatively minor lung collagen (8,14,40), and 2) a decrease in the major lung collagen type I [col(I)] (2, 53). We have shown that prospective monitoring of patients with human lung transplant revealed a critical role of col(V)-specific cellular immunity in OB pathogenesis (14,40). Although overexpression of col(V), an otherwise quantitatively minor collagen, is involved in OB pathology, mechanisms leading to col(V) overexpression are unknown. Thus a mechanistic understanding of the triggers of col(V)...

The epithelial complement inhibitory proteins (CIPs) cluster of differentiation 46 and 55 (CD46 and CD55) regulate circulating immune complex-mediated complement activation in idiopathic pulmonary fibrosis (IPF). Our previous studies demonstrated that IL-17A mediates epithelial injury via transforming growth factor ␤1 (TGF-␤1) and down-regulates CIPs. In the current study, we examined the mechanistic role of TGF-␤1 in complement activationmediated airway epithelial injury in IPF pathogenesis. We observed lower epithelial CIP expression in IPF lungs compared to normal lungs, associated with elevated levels of complement component 3a and 5a (C3a and C5a), locally and systemically. In normal primary human small airway epithelial cells ( Idiopathic pulmonary fibrosis (IPF) is a disease of high mortality for which lung transplantation is considered the only definitive therapy. Its pathogenesis remains largely unknown (1), but emerging concepts point to repeated injury to bronchiole-like epithelial cells and hyperplastic type II alveolar epithelial cells lining areas of honeycomb fibrosis (1, 2). These injured epithelial cells produce key profibrotic factors, including transforming growth factor ␤ (TGF-␤), which is implicated in epithelial injury (3-5) and epithelial-tomesenchymal transition (EMT; refs. 6, 7).The complement system is an integral arm of innate and adaptive immunity. Early studies demonstrated evidence of circulating immune complexes (8) and complement activation (9) in patients with IPF. In experimental models of IPF, antifibrotic effects due to deletion of complete downstream complement factors (10), specifically complement component 5 (C5; ref. 11), were reported. C3a and C5a are implicated in autoimmune diseases (12), chronic lung transplant rejection (13), experimental allergic asthma (14), and Abbreviations: ATII, alveolar type II; C3a, complement component 3a; C3aR, complement component 3a receptor; C5a, complement component 5a; C5aR, complement component 5a receptor; CD46, cluster of differentiation 46; CD55, cluster of differentiation 55; CIP, complement inhibitory protein; E-CAD, E-cadherin; EMT, epithelial-mesenchymal transition; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; IL-17A, interleukin-17A; IPF, idiopathic pulmonary fibrosis; p38MAPK, mitogen-activated protein kinase; PARP, poly(ADP-ribose) polymerase; PCR, polymerase chain reaction; RNAi, RNA interference; SABM, small airway basal medium; SAEC, small airway epithelial cell; siRNA, small interference RNA; SMAD7, mothers against decapentaplegic homolog 7; TGF-␤1, transforming growth factor ␤, isoform 1 4223 0892-6638/14/0028-4223 © FASEB wnloaded from www.fasebj.org by (158

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. FASEB J. 30, 2336–2350 (2016). http://www.fasebj.org

RationaleIdiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease characterized by progressive scarring and matrix deposition. Recent reports highlight an autoimmune component in IPF pathogenesis. We have reported anti-col(V) immunity in IPF patients. The objective of our study was to determine the specificity of col(V) expression profile and anti-col(V) immunity relative to col(I) in clinical IPF and the efficacy of nebulized col(V) in pre-clinical IPF models.MethodsCol(V) and col(I) expression profile was analyzed in normal human and IPF tissues. C57-BL6 mice were intratracheally instilled with bleomycin (0.025 U) followed by col(V) nebulization at pre-/post-fibrotic stage and analyzed for systemic and local responses.ResultsCompared to normal lungs, IPF lungs had higher protein and transcript expression of the alpha 1 chain of col(V) and col(I). Systemic anti-col(V) antibody concentrations, but not of anti-col(I), were higher in IPF patients. Nebulized col(V), but not col(I), prevented bleomycin-induced fibrosis, collagen deposition, and myofibroblast differentiation. Col(V) treatment suppressed systemic levels of anti-col(V) antibodies, IL-6 and TNF-α; and local Il-17a transcripts. Compared to controls, nebulized col(V)-induced tolerance abrogated antigen-specific proliferation in mediastinal lymphocytes and production of IL-17A, IL-6, TNF-α and IFN-γ. In a clinically relevant established fibrosis model, nebulized col(V) decreased collagen deposition. mRNA array revealed downregulation of genes specific to fibrosis (Tgf-β, Il-1β, Pdgfb), matrix (Acta2, Col1a2, Col3a1, Lox, Itgb1/6, Itga2/3) and members of the TGF-β superfamily (Tgfbr1/2, Smad2/3, Ltbp1, Serpine1, Nfkb/Sp1/Cebpb).ConclusionsAnti-col(V) immunity is pathogenic in IPF, and col(V)-induced tolerance abrogates bleomycin-induced fibrogenesis and down regulates TGF- β-related signaling pathways.