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1.  Role of Semaphorin 7a signaling in TGF-β1 induced lung fibrosis and scleroderma-related interstitial lung disease 
Arthritis and rheumatism  2011;63(8):2484-2494.
Semaphorin (Sema) 7a regulates TGF- β1 induced fibrosis. Using a murine model of pulmonary fibrosis in which an inducible, bioactive form of the human TGF- β1 gene is overexpressed in the lung, we tested the hypothesis that Sema-7a exerts its pro-fibrotic effects in part by promoting the tissue accumulation of CD45+ fibrocytes.
Fibrosis and fibrocytes were evaluated in TGF- β1 transgenic mice in which the Sema-7a locus had been disrupted. The effect of replacement or deletion of Sema-7a on bone marrow derived cells was ascertained using bone marrow transplantation. The role of the Sema-7a receptor β1 integrin was assessed using neutralizing antibodies. The applicability of these findings to TGF-β1-driven fibrosis in humans was examined in patients with scleroderma-related interstitial lung disease.
The appearance of fibrocytes in the lungs in TGF- β1 transgenic mice requires Sema-7a. Replacement of Sema-7a in bone marrow derived cells restores lung fibrosis and fibrocytes. Immunoneutralization of β1 integrin reduces pulmonary fibrocytes and fibrosis. Peripheral blood mononuclear cells from patients with scleroderma-related interstitial lung disease show increased mRNA for Sema-7a and the β1 integrin, with Sema-7a located on collagen producing fibrocytes and CD19+ lymphocytes. Peripheral blood fibrocyte outgrowth is enhanced in these patients. Stimulation of normal human peripheral blood mononuclear cells with recombinant Sema-7a enhances fibrocyte differentiation; these effects are attenuated by β1 integrin neutralization.
Interventions that reduce Sema-7a expression or prevent the Sema-7a - β1 integrin interaction may be ameliorative in TGF- β1-driven or fibrocyte-associated autoimmune fibroses.
PMCID: PMC3651701  PMID: 21484765
2.  Local apoptosis promotes collagen production by monocyte-derived cells in transforming growth factor β1-induced lung fibrosis 
Collagen-containing leukocytes (CD45+Col-I+) accumulate in diseased and fibrotic tissues. However, the precise identity of these cells and whether injury is required for their recruitment remain unknown. Using a murine model of pulmonary fibrosis in which an inducible, bioactive form of the human transforming growth factor (TGF)-β1 gene is targeted to the lung, we characterized the cell surface phenotype of collagen-containing CD45+ cells in the lung and tested the hypothesis that apoptotic cell death responses are essential to the accumulation of CD45+Col-I+ cells.
Our studies demonstrate that CD45+Col-I+ cells appearing in the TGF-β1-exposed murine lung express markers of the monocyte lineage. Inhibition of apoptosis via pharmacological caspase blockade led to a significant reduction in CD45+Col-I+ cells, which appear to accumulate independently of alternatively activated macrophages. There are also increased levels of apoptosis and greater numbers of CD45+Col-I+ in the lung tissue of patients with two distinct forms of fibrotic lung disease, idiopathic pulmonary fibrosis and connective tissue disease-related interstitial lung disease, when compared to lung from healthy normal controls. These findings are accompanied by an increase in collagen production in cultured monocytes obtained from subjects with fibrotic lung disease. Treatment of these cultured cells with the caspase inhibitor carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone (Z-VAD/fmk) reduces both apoptosis and collagen production in all subjects.
Interventions that prevent collagen production by monocytes via modulation of caspase activation and of apoptosis may be ameliorative in monocyte-associated, TGF-β1-driven processes such as pulmonary fibrosis.
PMCID: PMC3123188  PMID: 21586112
3.  Endogenous IL-11 Signaling Is Essential in Th2- and IL-13–Induced Inflammation and Mucus Production 
IL-11 and IL-11 receptor (R)α are induced by Th2 cytokines. However, the role(s) of endogenous IL-11 in antigen-induced Th2 inflammation has not been fully defined. We hypothesized that IL-11, signaling via IL-11Rα, plays an important role in aeroallergen-induced Th2 inflammation and mucus metaplasia. To test this hypothesis, we compared the responses induced by the aeroallergen ovalbumin (OVA) in wild-type (WT) and IL-11Rα–null mutant mice. We also generated and defined the effects of an antagonistic IL-11 mutein on pulmonary Th2 responses. Increased levels of IgE, eosinophilic tissue and bronchoalveolar lavage (BAL) inflammation, IL-13 production, and increased mucus production and secretion were noted in OVA-sensitized and -challenged WT mice. These responses were at least partially IL-11 dependent because each was decreased in mice with null mutations of IL-11Rα. Importantly, the administration of the IL-11 mutein to OVA-sensitized mice before aerosol antigen challenge also caused a significant decrease in OVA-induced inflammation, mucus responses, and IL-13 production. Intraperitoneal administration of the mutein to lung-specific IL-13–overexpressing transgenic mice also reduced BAL inflammation and airway mucus elaboration. These studies demonstrate that endogenous IL-11R signaling plays an important role in antigen-induced sensitization, eosinophilic inflammation, and airway mucus production. They also demonstrate that Th2 and IL-13 responses can be regulated by interventions that manipulate IL-11 signaling in the murine lung.
PMCID: PMC2586049  PMID: 18617680
IL-11; mutein; airway inflammation; mucus; IL-13
4.  Role of CCR5 in IFN-γ–induced and cigarette smoke–induced emphysema 
Journal of Clinical Investigation  2005;115(12):3460-3472.
Th1 inflammation and remodeling characterized by tissue destruction frequently coexist in human diseases. To further understand the mechanisms of these responses, we defined the role(s) of CCR5 in the pathogenesis of IFN-γ–induced inflammation and remodeling in a murine emphysema model. IFN-γ was a potent stimulator of the CCR5 ligands macrophage inflammatory protein–1α/CCL-3 (MIP-1α/CCL-3), MIP-1β/CCL-4, and RANTES/CCL-5, among others. Antibody neutralization or null mutation of CCR5 decreased IFN-γ–induced inflammation, DNA injury, apoptosis, and alveolar remodeling. These interventions decreased the expression of select chemokines, including CCR5 ligands and MMP-9, and increased levels of secretory leukocyte protease inhibitor. They also decreased the expression and/or activation of Fas, FasL, TNF, caspase-3, -8, and -9, Bid, and Bax. In accordance with these findings, cigarette smoke induced pulmonary inflammation, DNA injury, apoptosis, and emphysema via an IFN-γ–dependent pathway(s), and a null mutation of CCR5 decreased these responses. These studies demonstrate that IFN-γ is a potent stimulator of CC and CXC chemokines and highlight the importance of CCR5 in the pathogenesis of IFN-γ–induced and cigarette smoke–induced inflammation, tissue remodeling, and emphysema. They also demonstrate that CCR5 is required for optimal IFN-γ stimulation of its own ligands, other chemokines, MMPs, caspases, and cell death regulators and the inhibition of antiproteases.
PMCID: PMC1280966  PMID: 16284650
5.  Bcl-2–related protein A1 is an endogenous and cytokine-stimulated mediator of cytoprotection in hyperoxic acute lung injury 
Journal of Clinical Investigation  2005;115(4):1039-1048.
Hyperoxic acute lung injury (HALI) is characterized by a cell death response with features of apoptosis and necrosis that is inhibited by IL-11 and other interventions. We hypothesized that Bfl-1/A1, an antiapoptotic Bcl-2 protein, is a critical regulator of HALI and a mediator of IL-11–induced cytoprotection. To test this, we characterized the expression of A1 and the oxygen susceptibility of WT and IL-11 Tg(+) mice with normal and null A1 loci. In WT mice, 100% O2 caused TUNEL+ cell death, induction and activation of intrinsic and mitochondrial-death pathways, and alveolar protein leak. Bcl-2 and Bcl-xl were also induced as an apparent protective response. A1 was induced in hyperoxia, and in A1-null mice, the toxic effects of hyperoxia were exaggerated, Bcl-2 and Bcl-xl were not induced, and premature death was seen. In contrast, IL-11 stimulated A1, diminished the toxic effects of hyperoxia, stimulated Bcl-2 and Bcl-xl, and enhanced murine survival in 100% O2. In A1-null mice, IL-11–induced protection, survival advantage, and Bcl-2 and Bcl-xl induction were significantly decreased. VEGF also conferred protection via an A1-dependent mechanism. In vitro hyperoxia also stimulated A1, and A1 overexpression inhibited oxidant-induced epithelial cell apoptosis and necrosis. A1 is an important regulator of oxidant-induced lung injury, apoptosis, necrosis, and Bcl-2 and Bcl-xl gene expression and a critical mediator of IL-11– and VEGF-induced cytoprotection.
PMCID: PMC1070412  PMID: 15841185
6.  Overlapping and enzyme-specific contributions of matrix metalloproteinases-9 and -12 in IL-13–induced inflammation and remodeling 
IL-13 potently stimulates eosinophilic and lymphocytic inflammation and alveolar remodeling in the lung, effects that depend on the induction of various matrix metalloproteinases (MMPs). Here, we compared the remodeling and inflammatory effects of an IL-13 transgene in lungs of wild-type, MMP-9–deficient, or MMP-12–deficient mice. IL-13–induced alveolar enlargement, lung enlargement, compliance alterations, and respiratory failure and death were markedly decreased in the absence of MMP-9 or MMP-12. Moreover, IL-13 potently induced MMPs-2, -12, -13, and -14 in the absence of MMP-9, while induction of MMPs-2, -9, -13, and -14 by IL-13 was diminished in the absence of MMP-12. A deficiency in MMP-9 did not alter eosinophil, macrophage, or lymphocyte recovery, but increased the recovery of total leukocytes and neutrophils in bronchoalveolar lavage (BAL) fluids from IL-13 transgenic mice. In contrast, a deficiency in MMP-12 decreased the recovery of leukocytes, eosinophils, and macrophages, but not lymphocytes or neutrophils. These studies demonstrate that IL-13 acts via MMPs-9 and -12 to induce alveolar remodeling, respiratory failure, and death and that IL-13 induction of MMPs-2, -9, -13, and -14 is mediated at least partially by an MMP-12–dependent pathway. The also demonstrate that MMPs-9 and -12 play different roles in the generation of IL-13–induced inflammation, with MMP-9 inhibiting neutrophil accumulation and MMP-12 contributing to the accumulation of eosinophils and macrophages.
PMCID: PMC150413  PMID: 12189240
7.  Interleukin-13 Induces Tissue Fibrosis by Selectively Stimulating and Activating Transforming Growth Factor β1 
Interleukin (IL)-13 is a key mediator of tissue fibrosis caused by T helper cell type 2 inflammation. We hypothesized that the fibrogenic effects of IL-13 are mediated by transforming growth factor (TGF)-β. To test this hypothesis we compared the regulation of TGF-β in lungs from wild-type mice and CC10-IL-13 mice in which IL-13 overexpression causes pulmonary fibrosis. IL-13 selectively stimulated TGF-β1 production in transgenic animals and macrophages were the major site of TGF-β1 production and deposition in these tissues. IL-13 also activated TGF-β1 in vivo. This activation was associated with decreased levels of mRNA encoding latent TGF-β–binding protein-1 and increased mRNA encoding urinary plasminogen activator, matrix metalloproteinase (MMP)-9, and CD44. TGF-β1 activation was abrogated by the plasmin/serine protease antagonist aprotinin. It was also decreased in progeny of crosses of CC10-IL-13 mice and MMP-9 null mice but was not altered in crosses with CD44 null animals. IL-13–induced fibrosis was also significantly ameliorated by treatment with the TGF-β antagonist soluble TGFβR-Fc (sTGFβR-Fc). These studies demonstrate that IL-13 is a potent stimulator and activator of TGF-β1 in vivo. They also demonstrate that this activation is mediated by a plasmin/serine protease- and MMP-9–dependent and CD44-independent mechanism(s) and that the fibrogenic effects of IL-13 are mediated, in great extent, by this TGF-β pathway.
PMCID: PMC2195954  PMID: 11560996
lung; plasmin; matrix metalloproteinase-9; CD44; asthma
8.  IL-13 stimulates vascular endothelial cell growth factor and protects against hyperoxic acute lung injury 
Hyperoxia is an important cause of acute lung injury. To determine whether IL-13 is protective in hyperoxia, we compared the survival in 100% O2 of transgenic mice that overexpress IL-13 in the lung and of nontransgenic littermate controls. IL-13 enhanced survival in 100% O2. One hundred percent of nontransgenic mice died in 4–5 days, whereas 100% of IL-13–overexpressing mice lived for more than 7 days, and many lived 10–14 days. IL-13 also stimulated VEGF accumulation in mice breathing room air, and it interacted with 100% 2 to increase VEGF accumulation further. The 164–amino acid isoform was the major VEGF moiety in bronchoalveolar lavage from transgenic mice in room air, whereas the 120– and 188–amino acid isoforms accumulated in these mice during hyperoxia. In addition, antibody neutralization of VEGF decreased the survival of IL-13–overexpressing mice in 100% 2. These studies demonstrate that IL-13 has protective effects in hyperoxic acute lung injury. They also demonstrate that IL-13, alone and in combination with 100% 2, stimulates pulmonary VEGF accumulation, that this stimulation is isoform-specific, and that the protective effects of IL-13 are mediated, in part, by VEGF.
PMCID: PMC381393  PMID: 10995789
9.  Pulmonary expression of interleukin-13 causes inflammation, mucus hypersecretion, subepithelial fibrosis, physiologic abnormalities, and eotaxin production 
Journal of Clinical Investigation  1999;103(6):779-788.
Interleukin (IL)-13 is a pleiotropic cytokine produced in large quantities by activated CD4+ Th2 lymphocytes. To define further its potential in vivo effector functions, the Clara cell 10-kDa protein promoter was used to express IL-13 selectively in the lung, and the phenotype of the resulting transgenic mice was characterized. In contrast to transgene-negative littermates, the lungs of transgene-positive mice contained an inflammatory response around small and large airways and in the surrounding parenchyma. It was mononuclear in nature and contained significant numbers of eosinophils and enlarged and occasionally multinucleated macrophages. Airway epithelial cell hypertrophy, mucus cell metaplasia, the hyperproduction of neutral and acidic mucus, the deposition of Charcot-Leyden–like crystals, and subepithelial airway fibrosis were also prominently noted. Eotaxin protein and mRNA were also present in large quantities in the lungs of the transgene-positive, but not the transgene-negative, mice. IL-4, IL-5, granulocyte-macrophage colony-stimulating factor, and monocyte chemoattractant protein-5 were not similarly detected. Physiological evaluations revealed significant increases in baseline airways resistance and airways hyperresponsiveness (AHR) to methacholine in transgene-positive animals. Thus, the targeted pulmonary expression of IL-13 causes a mononuclear and eosinophilic inflammatory response, mucus cell metaplasia, the deposition of Charcot-Leyden–like crystals, airway fibrosis, eotaxin production, airways obstruction, and nonspecific AHR. IL-13 may play an important role in the pathogenesis of similar responses in asthma or other Th2-polarized tissue responses.
PMCID: PMC408149  PMID: 10079098

Results 1-9 (9)