Proteoglycan expression in bleomycin lung fibroblasts: role of transforming growth factor-beta(1) and interferon-gamma

In dystrophic mdx hindlimb muscles where fibrosis is limited, versican haploinsufficiency transiently improves contractile function without reducing inflammation

Versican is increased with inflammation and fibrosis, and is upregulated in Duchenne muscular dystrophy. In fibrotic diaphragm muscles from dystrophic mdx mice, genetic reduction of versican attenuated macrophage infiltration and improved contractile function. Versican is also implicated in myogenesis. Here, we investigated whether versican modulated mdx hindlimb muscle pathology, where inflammation and regeneration are increased but fibrosis is minimal. Immunohistochemistry and qRT-PCR were used to assess how fiber type and glucocorticoids (α-methylprednisolone) modify versican expression. To genetically reduce versican, female mdx and male versican haploinsufficient (hdf) mice were bred resulting in male mdx-hdf and mdx (control) pups. Versican expression, contractile function, and pathology were evaluated in hindlimb muscles. Versican immunoreactivity was greater in slow versus fast hindlimb muscles. Versican mRNA transcripts were reduced by α-methylprednisolone in soleus, but not in fast extensor digitorum longus, muscles. In juvenile (6-wk-old) mdx-hdf mice, versican expression was most robustly decreased in soleus muscles leading to improved force output and a modest reduction in fatiguability. These functional benefits were not accompanied by decreased inflammation. Muscle architecture, regeneration markers, and fiber type also did not differ between mdx-hdf mice and mdx littermates. Improvements in soleus contractile function were not retained in adult (20-wk-old) mdx-hdf mice. In conclusion, soleus muscles from juvenile mdx mice were most responsive to pharmacological or genetic approaches targeting versican; however, the benefits of versican reduction were limited due to low fibrosis. Preclinical matrix research in dystrophy should account for muscle phenotype (including age) and the interdependence between inflammation and fibrosis. NEW & NOTEWORTHY The proteoglycan versican is upregulated in muscular dystrophy. In fibrotic diaphragm muscles from mdx mice, versican reduction attenuated macrophage infiltration and improved performance. Here, in hindlimb muscles from 6- and 20-wk-old mdx mice, where pathology is mild, versican reduction did not decrease inflammation and contractile function improvements were limited to juvenile mice. In dystrophic mdx muscles, the association between versican and inflammation is mediated by fibrosis, demonstrating interdependence between the immune system and extracellular matrix.

Biomimetic strategies for the deputization of proteoglycan functions

Proteoglycans (PGs), which have glycosaminoglycan chains attached to their protein cores, are essential for maintaining the morphology and function of healthy body tissues. Extracellular PGs perform various functions, classified into the following four categories: i) the modulation of tissue mechanical properties; ii) the regulation and protection of the extracellular matrix; iii) protein sequestration; and iv) the regulation of cell signaling. The depletion of PGs may significantly impair tissue function, encompassing compromised mechanical characteristics and unregulated inflammatory responses. Since PGs play critical roles in the function of healthy tissues and their synthesis is complex, the development of PG mimetic molecules that recapitulate PG functions for tissue engineering and therapeutic applications has attracted the interest of researchers for more than 20 years. These approaches have ranged from semisynthetic graft copolymers to recombinant PG domains produced by cells that have undergone genetic modifications. This review discusses some essential extracellular PG functions and approaches to mimicking these functions.

Immune Mechanisms of Pulmonary Fibrosis with Bleomycin

Fibrosis and structural remodeling of the lung tissue can significantly impair lung function, often with fatal consequences. The etiology of pulmonary fibrosis (PF) is diverse and includes different triggers such as allergens, chemicals, radiation, and environmental particles. However, the cause of idiopathic PF (IPF), one of the most common forms of PF, remains unknown. Experimental models have been developed to study the mechanisms of PF, and the murine bleomycin (BLM) model has received the most attention. Epithelial injury, inflammation, epithelial-mesenchymal transition (EMT), myofibroblast activation, and repeated tissue injury are important initiators of fibrosis. In this review, we examined the common mechanisms of lung wound-healing responses after BLM-induced lung injury as well as the pathogenesis of the most common PF. A three-stage model of wound repair involving injury, inflammation, and repair is outlined. Dysregulation of one or more of these three phases has been reported in many cases of PF. We reviewed the literature investigating PF pathogenesis, and the role of cytokines, chemokines, growth factors, and matrix feeding in an animal model of BLM-induced PF.

A Role for HAPLN1 During Phenotypic Modulation of Human Lung Fibroblasts In Vitro

Hyaluronan and proteoglycan link protein 1 (HAPLN1) stabilizes interactions between two important extracellular matrix (ECM) macromolecules, versican and hyaluronan, which facilitate proliferation of fibroblasts and their conversion to myofibroblasts. However, the role of HAPLN1 in these events has not been studied. Using immunocytochemistry, cellular and ECM locations of HAPLN1 were evaluated in cultured human lung fibroblasts during proliferation and conversion to myofibroblasts. HAPLN1 localized to pericellular matrices, associating with both versican and hyaluronan in the ECM and on the cell surface. Nuclear and total HAPLN1 immunostaining increased after myofibroblast induction. Confocal microscopy showed HAPLN1 predominant in the ECM under cells while versican predominated above cells. Versican and HAPLN1 were also juxtaposed in columnar inclusions in the cytoplasm and nucleus. Nuclear HAPLN1 staining in interphase cells redistributed to the cytosol during mitosis. In the absence of TGF-β1, addition of exogenous bovine HAPLN1 (together with aggrecan G1) facilitated myofibroblast formation, as seen by significant upregulation of α-smooth muscle actin (SMA) staining, while adding full-length bovine versican had no effect. Increased compaction of hyaluronan-rich ECM suggests that HAPLN1 plus G1 addition affects hyaluronan networks and myofibroblast formation. These observations demonstrate changes in both extracellular and intracellular localization of HAPLN1 during fibroblast proliferation and myofibroblast conversion suggesting a possible role in fibrotic remodeling.

Respiratory exposure to nano-TiO2 induces pulmonary toxicity in mice involving reactive free radical-activated TGF-β/Smad/p38MAPK/Wnt pathways

Numerous studies have shown that lung injury can be caused by respiratory exposure to nanoparticulate titanium dioxide (nano-TiO₂ ), but whether pulmonary inflammation and fibrosis are related to the activation of the TGF-β/Smad/p38MAPK/Wnt pathways remains unclear. In this study, mice were administrated nano-TiO₂ by nasal instillation for nine consecutive months, and the molecular mechanisms of nano-TiO₂ on the pulmonary toxicity of mice were examined. The findings suggested that nano-TiO₂ caused pneumonia and pulmonary fibrosis. Furthermore, the results also showed that an overproduction of reactive free radicals occurred in mouse lungs, and that the expression of TGF-β/p38MAPK/Wnt pathway-related factors, including hypoxia-inducible factor 1α (HIF-1α), transforming growth factor-β1 (TGF-β1), phosphorylated p38 mitogen activated protein kinases (p-p38MAPK), small mothers against decapentaplegic homolog 2 (Smad2), extracellular matrix (ECM), Wingless/Integrated 3 (Wnt3), Wingless/Integrated 4 (Wnt4), integrin-linked kinase (ILK), β-catenin, nuclear factor-κB (NF-κB), α-smooth muscle actin (α-SMA), c-Myc, Type I collage (collagen I), and Type collage III (collagen III) were remarkably elevated, while phosphorylated glycogen synthase kinase-3β (p-GSK-3β) expression was decreased. Those data implied that the pulmonary inflammation and fibrosis caused by nano-TiO₂ exposure may be involved in reactive free radical-mediated activation of the TGF-β/Smad/p38MAPK/Wnt pathways.

Quantitative proteomic profiling of extracellular matrix and site-specific collagen post-translational modifications in an in vitro model of lung fibrosis

Lung fibrosis is characterized by excessive deposition of extracellular matrix (ECM), in particular collagens, by fibroblasts in the interstitium. Transforming growth factor-β1 (TGF-β1) alters the expression of many extracellular matrix (ECM) components produced by fibroblasts, but such changes in ECM composition as well as modulation of collagen post-translational modification (PTM) levels have not been comprehensively investigated. Here, we performed mass spectrometry (MS)-based proteomics analyses to assess changes in the ECM deposited by cultured lung fibroblasts from idiopathic pulmonary fibrosis (IPF) patients upon stimulation with transforming growth factor β1 (TGF-β1). In addition to the ECM changes commonly associated with lung fibrosis, MS-based label-free quantification revealed profound effects on enzymes involved in ECM crosslinking and turnover as well as multiple positive and negative feedback mechanisms of TGF-β1 signaling. Notably, the ECM changes observed in this in vitro model correlated significantly with ECM changes observed in patient samples. Because collagens are subject to multiple PTMs with major implications in disease, we implemented a new bioinformatic platform to analyze MS data that allows for the comprehensive mapping and site-specific quantitation of collagen PTMs in crude ECM preparations. These analyses yielded a comprehensive map of prolyl and lysyl hydroxylations as well as lysyl glycosylations for 15 collagen chains. In addition, site-specific PTM analysis revealed novel sites of prolyl-3-hydroxylation and lysyl glycosylation in type I collagen. Interestingly, the results show, for the first time, that TGF-β1 can modulate prolyl-3-hydroxylation and glycosylation in a site-specific manner. Taken together, this proof of concept study not only reveals unanticipated TGF-β1 mediated regulation of collagen PTMs and other ECM components but also lays the foundation for dissecting their key roles in health and disease.

The proteomic data has been deposited to the ProteomeXchange Consortium via the MassIVE partner repository with the data set identifier MSV000082958.

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Quantitative proteomics of TGF-β-induced changes in ECM composition and collagen PTM in pulmonary fibroblasts

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TGF-β promotes crosslinking and turnover as well as complex feedback mechanisms that alter fibroblast ECM homeostasis.

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A novel bioinformatic workflow for MS data analysis enabled global mapping and quantitation of known and novel collagen PTMs

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Quantitative assessment of prolyl-3-hydroxylation site occupancy and lysine-O-glycosylation microheterogeneity

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TGF-β1 modulates collagen PTMs in a site-specific manner that may favor collagen accumulation in lung fibrosis

5-HT2 and 5-HT2B antagonists attenuate pro-fibrotic phenotype in human adult dermal fibroblasts by blocking TGF-β1 induced non-canonical signaling pathways including STAT3 : implications for fibrotic diseases like scleroderma

BACKGROUND

Release of 5-hydroxytryptamine (5-HT; serotonin) from activated platelets following microvascular injury leads to tissue fibrosis. 5-HT strongly induces extracellular matrix synthesis in dermal fibroblasts in a transforming growth factor beta 1 (TGF-β1)-dependent manner.

AIM

To evaluate anti-fibrotic properties of inhibitors of 5-HT₂ and 5-HT_2B (terguride, SB204741) respectively in human adult dermal fibroblasts (HADF) derived from a patient with scleroderma.

METHODS

Anti-fibrotic efficacy of 5-HT₂ and 5-HT_2B inhibitors was evaluated as per two strategies: HADF were incubated with 5-HT (1 μM)/TGF-β1 (10 ng/mL) for 1 hour followed by 5-HT (1 μM)/TGF-β1 (10 ng/mL) and terguride or SB204741 (1 μM, each) for 24 hours (post-treatment strategy) and HADF were treated with terguride or SB204741 (1 μM, each) for 1 hour followed by 5-HT (1 μM)/TGF-β1 (10 ng/mL) for 24 hours (pre-treatment strategy). Real time quantitative polymerase chain reaction for expression of pro-fibrotic (TGFΒ1, COL1A1, COL1A2, ACTA2, CTGF and FN1) and anti-fibrotic genes (MMP2/TIMP1) was performed. Expression of type I collagen, alpha smooth muscle actin (α-SMA), phosphorylation of Smad3, ERK1/2 and STAT3 was examined by immunoblotting.

RESULTS

Stimulation of HADF cells with 5-HT/TGF-β1 led to the increased expression of pro-fibrotic genes which was significantly reduced by both terguride and SB204741. Expression of anti-fibrotic genes was not affected upon incubation with the inhibitors. In 5-HT-stimulated HADF, treatment with terguride and SB204741 decreased type I collagen and α-SMA. In 5-HT/TGF-β1 stimulated HADF, terguride and SB204741 treatment reduced ERK1/2 and STAT3 phosphorylation but did not influence Smad3 phosphorylation.

CONCLUSION

Terguride and SB204741 reduce pro-fibrotic potential of HADF cells and suppress TGF-β1-mediated non-canonical pathways, ERK1/2 and STAT3 which have been implicated in the regulation of pro-fibrotic genes and in the development of fibrosis. Taken together, our data suggest that 5-HT inhibitors might reduce fibrosis via suppression of TGF-beta1-mediated non-canonical signaling pathways. These observations have important therapeutic implications for fibrotic disorders like scleroderma.

Proteoglycans as Immunomodulators of the Innate Immune Response to Lung Infection

Proteoglycans (PGs) are complex, multifaceted molecules that participate in diverse interactions vital for physiological and pathological processes. As structural components, they provide a scaffold for cells and structural organization that helps define tissue architecture. Through interactions with water, PGs enable molecular and cellular movement through tissues. Through selective ionic interactions with growth factors, chemokines, cytokines, and proteases, PGs facilitate the ability of these soluble ligands to regulate intracellular signaling events and to influence the inflammatory response. In addition, recent findings now demonstrate that PGs can activate danger-associated molecular patterns (DAMPs) and other signaling pathways to influence production of many of these soluble ligands, indicating a more direct role for PGs in influencing the immune response and tissue inflammation. This review will focus on PGs that are selectively expressed during lung inflammation and will examine the novel emerging concept of PGs as immunomodulatory regulators of the innate immune responses in lungs.

5-HT2B receptor antagonists attenuate myofibroblast differentiation and subsequent fibrotic responses in vitro and in vivo

Pulmonary fibrosis is characterized by excessive accumulation of connective tissue, along with activated extracellular matrix (ECM)‐producing cells, myofibroblasts. The pathological mechanisms are not well known, however serotonin (5‐HT) and 5‐HT class 2 (5‐HT₂) receptors have been associated with fibrosis. The aim of the present study was to investigate the role of 5‐HT_2B receptors in fibrosis, using small molecular 5‐HT_2B receptor antagonists EXT5 and EXT9, with slightly different receptor affinity. Myofibroblast differentiation [production of alpha‐smooth muscle actin (α‐SMA)] and ECM synthesis were quantified in vitro, and the effects of the receptor antagonists were evaluated. Pulmonary fibrosis was also modeled in mice by subcutaneous bleomycin administrations (under light isoflurane anesthesia), and the effects of receptor antagonists on tissue density, collagen‐producing cells, myofibroblasts and decorin expression were investigated. In addition, cytokine expression was analyzed in serum. Lung fibroblasts displayed an increased α‐SMA (P < 0.05) and total proteoglycan production (P < 0.01) when cultured with TGF‐β1 together with 5‐HT, which were significantly reduced with both receptor antagonists. Following treatment with EXT5 or EXT9, tissue density, expression of decorin, number of collagen‐producing cells, and myofibroblasts were significantly decreased in vivo compared to bleomycin‐treated mice. Receptor antagonization also significantly reduced systemic levels of TNF‐α and IL‐1β, indicating a role in systemic inflammation. In conclusion, 5‐HT_2B receptor antagonists have potential to prevent myofibroblast differentiation, in vitro and in vivo, with subsequent effect on matrix deposition. The attenuating effects of 5‐HT_2B receptor antagonists on fibrotic tissue remodeling suggest these receptors as novel targets for the treatment of pulmonary fibrosis.

Targeting of Proteoglycan Synthesis Pathway: A New Strategy to Counteract Excessive Matrix Proteoglycan Deposition and Transforming Growth Factor-β1-Induced Fibrotic Phenotype in Lung Fibroblasts

Stimulation of proteoglycan (PG) synthesis and deposition plays an important role in the pathophysiology of fibrosis and is an early and dominant feature of pulmonary fibrosis. Transforming growth factor-β1 (TGF-β1) is a major cytokine associated with fibrosis that induces excessive synthesis of matrix proteins, particularly PGs. Owing to the importance of PGs in matrix assembly and in mediating cytokine and growth factor signaling, a strategy based on the inhibition of PG synthesis may prevent excessive matrix PG deposition and attenuates profibrotic effects of TGF-β1 in lung fibroblasts. Here, we showed that 4-MU4-deoxy-β-D-xylopyranoside, a competitive inhibitor of β4-galactosyltransferase7, inhibited PG synthesis and secretion in a dose-dependent manner by decreasing the level of both chondroitin/dermatan- and heparin-sulfate PG in primary lung fibroblasts. Importantly, 4-MU4-deoxy-xyloside was able to counteract TGF-β1-induced synthesis of PGs, activation of fibroblast proliferation and fibroblast-myofibroblast differentiation. Mechanistically, 4-MU4-deoxy-xyloside treatment inhibited TGF-β1-induced activation of canonical Smads2/3 signaling pathway in lung primary fibroblasts. The knockdown of β4-galactosyltransferase7 mimicked 4-MU4-deoxy-xyloside effects, indicating selective inhibition of β4-galactosyltransferase7 by this compound. Collectively, this study reveals the anti-fibrotic activity of 4-MU4-deoxy-xyloside and indicates that inhibition of PG synthesis represents a novel strategy for the treatment of lung fibrosis.

Hyaluronan, a crucial regulator of inflammation

Hyaluronan (HA), a major component of the extracellular matrix (ECM), plays a key role in regulating inflammation. Inflammation is associated with accumulation and turnover of HA polymers by multiple cell types. Increasingly through the years, HA has become recognized as an active participant in inflammatory, angiogenic, fibrotic, and cancer promoting processes. HA and its binding proteins regulate the expression of inflammatory genes, the recruitment of inflammatory cells, the release of inflammatory cytokines, and can attenuate the course of inflammation, providing protection against tissue damage. A growing body of evidence suggests the cell responses are HA molecular weight dependent. HA fragments generated by multiple mechanisms throughout the course of inflammatory pathologies, elicit cellular responses distinct from intact HA. This review focuses on the role of HA in the promotion and resolution of inflammation.

Glycosyltransferases and glycosaminoglycans in bleomycin and transforming growth factor-β1-induced pulmonary fibrosis

Glycosaminoglycan (GAG) chains of proteoglycans (PGs) play important roles in fibrosis through cell-matrix interactions and growth factor binding in the extracellular matrix. We investigated the expression and regulation of PG core protein (versican) and key enzymes (xylosyltransferase [XT]-I, β1,3-glucuronosyltransferase [GlcAT]-I, chondroitin-4-sulfotransferase [C4ST]) implicated in synthesis and sulfation of GAGs in bleomycin (BLM) and adenovirus-transforming growth factor (TGF)-β1-induced lung fibrosis in rats. We also studied the role of GlcAT-I or TGF-β1 and the signaling pathways regulating PG-GAG production in primary lung fibroblasts isolated from saline- or BLM-instilled rats. The mRNA for XT-I, GlcAT-I, C4ST, and versican was increased in the lung 14 days after BLM injury. In vitro studies indicate that fibrotic lung fibroblasts (FLFs) expressed more XT-I, C4ST, and chondroitin sulfate (CS)-GAGs than did normal lung fibroblasts at baseline. TGF-β1 enhanced the expression of XT-I, C4ST-I, and versican in normal lung fibroblasts, whereas SB203580 or SB431542, by targeting p38 mitogen-activated protein kinase or TGF-β type-1 receptor/activin receptor-like kinase 5, respectively, attenuated the response to both TGF-β1 and FLFs on PG-GAG expression. Neutralizing anti-TGF-β1 antibody abrogated FLF-conditioned medium-stimulated expression of XT-I, GlcAT-I, versican, and CS-GAG. Forced expression of TGF-β1 in vivo enhanced versican, XT-I, GlcAT-I, and C4ST-I expression and PG-GAG deposition in rat lungs. Finally, induced expression of GlcAT-I gene in rat lung fibroblasts increased GAG synthesis by these cells. Together, our results provide new insights into the basis for increased PG-GAG deposition in lung fibrosis; inhibition of TGF-β1-mediated or fibrosis-induced PG-GAG production by activin receptor-like kinase 5/p38 inhibitors may contribute to antifibrotic activity.

Versican is upregulated in circulating monocytes in patients with systemic sclerosis and amplifies a CCL2-mediated pathogenic loop

Introduction

Altered phenotypes of circulating monocytes of patients with systemic sclerosis (SSc) have been reported, but the role of these alterations in the pathogenesis of SSc remains unclear. This study was undertaken to identify molecules that are preferentially expressed by SSc monocytes, and to investigate the roles of these molecules in the pathogenic process of SSc.

Methods

We analyzed circulating CD14⁺ monocytes isolated from 36 patients with SSc and 32 healthy control subjects. The monocytes' gene expression profiles were assessed by Oligo GEArray^® (SABiosciences, Frederic, MA, USA) and semiquantitative or quantitative PCR; their protein expression was evaluated in culture supernatants of unstimulated monocytes by immunoblotting or ELISA, and by immunocytostaining. Monocyte chemoattractant activity of CCL2 was assessed in a TransWell^® system (Corning Incorporated, Corning, NY, USA) in the presence or absence of chondroitin sulfate (CS).

Results

A step-wise approach to profiling gene expression identified that versican and CCL2 were upregulated in SSc monocytes. Subsequent analysis of proteins expressed in monocyte culture supernatants confirmed enhanced production of versican and CCL2 in SSc monocytes compared with control monocytes. CCL2 bound to CS chains of versican and colocalized with versican in the monocytes' Golgi apparatus. Finally, CCL2 had a greater ability to mediate monocyte migration when bound to CS chains, because this binding provided efficient formation of CCL2 gradients and protection from protease attack.

Conclusion

Circulating monocytes with elevated versican and CCL2 levels may contribute to the fibrotic process in a subset of SSc patients by amplifying a positive feedback loop consisting of versican, CCL2, and the influx of monocytes.

Syndecan-2 is a novel target of insulin-like growth factor binding protein-3 and is over-expressed in fibrosis

Extracellular matrix deposition and tissue scarring characterize the process of fibrosis. Transforming growth factor beta (TGFβ) and Insulin-like growth factor binding protein-3 (IGFBP-3) have been implicated in the pathogenesis of fibrosis in various tissues by inducing mesenchymal cell proliferation and extracellular matrix deposition. We identified Syndecan-2 (SDC2) as a gene induced by TGFβ in an IGFBP-3-dependent manner. TGFβ induction of SDC2 mRNA and protein required IGFBP-3. IGFBP-3 independently induced production of SDC2 in primary fibroblasts. Using an ex-vivo model of human skin in organ culture expressing IGFBP-3, we demonstrate that IGFBP-3 induces SDC2 ex vivo in human tissue. We also identified Mitogen-activated protein kinase-interacting kinase (Mknk2) as a gene induced by IGFBP-3. IGFBP-3 triggered Mknk2 phosphorylation resulting in its activation. Mknk2 independently induced SDC2 in human skin. Since IGFBP-3 is over-expressed in fibrotic tissues, we examined SDC2 levels in skin and lung tissues of patients with systemic sclerosis (SSc) and lung tissues of patients with idiopathic pulmonary fibrosis (IPF). SDC2 levels were increased in fibrotic dermal and lung tissues of patients with SSc and in lung tissues of patients with IPF. This is the first report describing elevated levels of SDC2 in fibrosis. Increased SDC2 expression is due, at least in part, to the activity of two pro-fibrotic factors, TGFβ and IGFBP-3.

Inflammation amplification by Versican: the first mediator

The effects of inflammation may not always benefit the individual. Its amplifying nature represents a highly regulated biological program, and the inflammatory microenvironment is its essential component. Growing evidence suggests that the ECM (extracellular matrix) is important for the early steps of inflammation. Versican, a ubiquitous component of the ECM, contributes to the formation of the inflammatory response and is highly regulated by cytokines. Certain cytokines exert their initial effects on versican to alter the homeostasis of the inflammatory milieu, and inappropriate production of versican may promote the next inflammatory response. Therefore, versican could be the first step in the amplification of the inflammatory response, and ongoing research of this molecule may help to explain the pathogenesis of inflammation.

Proteoglycans: key regulators of pulmonary inflammation and the innate immune response to lung infection

Exposure to viruses and bacteria results in lung infections and places a significant burden on public health. The innate immune system is an early warning system that recognizes viruses and bacteria, which results in the rapid production of inflammatory mediators such as cytokines and chemokines and the pulmonary recruitment of leukocytes. When leukocytes emigrate from the systemic circulation through the extracellular matrix (ECM) in response to lung infection they encounter proteoglycans, which consist of a core protein and their associated glycosaminoglycans. In this review, we discuss how proteoglycans serve to modify the pulmonary inflammatory response and leukocyte migration through a number of different mechanisms including: (1) The ability of soluble proteoglycans or fragments of glycosaminoglycans to activate Toll-like receptor (TLRs) signaling pathways; (2) The binding and sequestration of cytokines, chemokines, and growth factors by proteoglycans; (3) the ability of proteoglycans and hyaluronan to facilitate leukocyte adhesion and sequestration; and (4) The interactions between proteoglycans and matrix metalloproteinases (MMP) that alter the function of these proteases. In conclusion, proteoglycans fine-tune tissue inflammation through a number of different mechanisms. Clarification of the mechanisms whereby proteoglycans modulate the pulmonary inflammatory response will most likely lead to new therapeutic approaches to inflammatory lung disease and lung infection.

Increased deposition of chondroitin/dermatan sulfate glycosaminoglycan and upregulation of β1,3-glucuronosyltransferase I in pulmonary fibrosis

Pulmonary fibrosis (PF) is characterized by increased deposition of proteoglycans (PGs), in particular core proteins. Glycosaminoglycans (GAGs) are key players in tissue repair and fibrosis, and we investigated whether PF is associated with changes in the expression and structure of GAGs as well as in the expression of β1,3-glucuronosyltransferase I (GlcAT-I), a rate-limiting enzyme in GAG synthesis. Lung biopsies from idiopathic pulmonary fibrosis (IPF) patients and lung tissue from a rat model of bleomycin (BLM)-induced PF were immunostained for chondroitin sulfated-GAGs and GlcAT-I expression. Alterations in disaccharide composition and sulfation of chondroitin/dermatan sulfate (CS/DS) were evaluated by fluorophore-assisted carbohydrate electrophoresis (FACE) in BLM rats. Lung fibroblasts isolated from control (saline-instilled) or BLM rat lungs were assessed for GAG structure and GlcAT-I expression. Disaccharide analysis showed that 4- and 6-sulfated disaccharides were increased in the lungs and lung fibroblasts obtained from fibrotic rats compared with controls. Fibrotic lung fibroblasts and transforming growth factor-β(1) (TGF-β(1))-treated normal lung fibroblasts expressed increased amounts of hyaluronan and 4- and 6-sulfated chondroitin, and neutralizing anti-TGF-β(1) antibody diminished the same. TGF-β(1) upregulated GlcAT-I and versican expression in lung fibroblasts, and signaling through TGF-β type I receptor/p38 MAPK was required for TGF-β(1)-mediated GlcAT-I and CS-GAG expression in fibroblasts. Our data show for the first time increased expression of CS-GAGs and GlcAT-I in IPF, fibrotic rat lungs, and fibrotic lung fibroblasts. These data suggest that alterations of sulfation isomers of CS/DS and upregulation of GlcAT-I contribute to the pathological PG-GAG accumulation in PF.

TGF-β: Titan of Lung Fibrogenesis

Pulmonary fibrosis is characterized by epithelial cell injury, accumulation of myofibroblasts, and excessive deposition of collagen and other extracellular matrix elements, leading to loss of pulmonary function. Studies in both humans and animal models strongly suggest that TGF-β1 plays a pivotal role in the pathogenesis of pulmonary fibrosis. This review will first give an overview of TGF-β signaling and the effects of its inhibition on lung fibrogenesis. This overview includes information on TGF-β signal transduction pathways, the importance of TGF-β in the accumulation of myofibroblasts, the role of TGF-β in epithelial injury and apoptosis, the role of TGF-β in extracellular matrix remodeling, and the effects of inhibiting TGF-β signaling in animal models of lung fibrosis. Subsequently this review will highlight recent advances in two areas of particular interest to our research group: (1) TGF-β and proteoglycans; (2) TGF-β and histone deacetylases. Although our understanding of the role of TGF-β and its mechanisms of action in lung fibrogenesis has increased dramatically in recent years, there is still much to be learned about this important molecule, especially how TGF-β function is modulated in vivo, and its complex interactions with other factors expressed during lung injury and repair. Research in these areas will help identify novel therapeutic targets for the treatment of pulmonary fibrosis that will hopefully improve the prognosis of this devastating illness.

A CD36 synthetic peptide inhibits silica-induced lung fibrosis in the mice

Silicosis is a kind of pneumoconiosis caused by inhalation of silica dust, which is characterized by lung fibrosis. The biologically active form of transforming growth factor-β1 (TGF-β1) plays a key role in the development of lung fibrosis. CD36 is involved in the transformation of latent TGF-β1 (L-TGF-β1) to active TGF-β1. The antagonistic effect of the synthetic peptide was analyzed by the administration of CD36 (93-110) synthetic peptide to the silicosis model of mice. The hydroxyproline content of the silica + CD36 (93-110) synthetic peptide group was significantly lower than that of the other experimental groups [silica and silica + CD36 (208-225) synthetic peptide groups] (p < .05). Inflammation, fibrotic degree and distribution of collagen fibers in silicotic nodules of the silica + CD36 (93-110) synthetic peptide group were less than those of the other experimental groups. The expressions of collagen I and III of the silica + CD36 (93-110) synthetic peptide group were significantly lower than those of the other experimental groups (p < .05). CD36 (93-110) synthetic peptide reduced the tissue fibrotic pathologies and collagen accumulation in the silicosis model of mice, resulting in the decreased severity of silica-induced lung fibrosis.

Lung parenchymal mechanics in health and disease

The mechanical properties of lung tissue are important determinants of lung physiological functions. The connective tissue is composed mainly of cells and extracellular matrix, where collagen and elastic fibers are the main determinants of lung tissue mechanical properties. These fibers have essentially different elastic properties, form a continuous network along the lungs, and are responsible for passive expiration. In the last decade, many studies analyzed the relationship between tissue composition, microstructure, and macrophysiology, showing that the lung physiological behavior reflects both the mechanical properties of tissue individual components and its complex structural organization. Different lung pathologies such as acute respiratory distress syndrome, fibrosis, inflammation, and emphysema can affect the extracellular matrix. This review focuses on the mechanical properties of lung tissue and how the stress-bearing elements of lung parenchyma can influence its behavior.

Silencing CD36 gene expression results in the inhibition of latent-TGF-beta1 activation and suppression of silica-induced lung fibrosis in the rat

Background

The biologically active form of transforming growth factor-β1 (TGF-β1) plays a key role in the development of lung fibrosis. CD36 is involved in the transformation of latent TGF-β1 (L-TGF-β1) to active TGF-β1. To clarify the role of CD36 in the development of silica-induced lung fibrosis, a rat silicosis model was used to observe both the inhibition of L-TGF-β1 activation and the antifibrotic effect obtained by lentiviral vector silencing of CD36 expression.

Methods

The rat silicosis model was induced by intratracheal injection of 10 mg silica per rat and CD36 expression was silenced by administration of a lentiviral vector (Lv-shCD36). The inhibition of L-TGF-β1 activation was examined using a CCL-64 mink lung epithelial growth inhibition assay, while determination of hydroxyproline content along with pathological and immunohistochemical examinations were used for observation of the inhibition of silica-induced lung fibrosis.

Results

The lentiviral vector (Lv-shCD36) silenced expression of CD36 in alveolar macrophages (AMs) obtained from bronchoalveolar lavage fluid (BALF) and the activation of L-TGF-β1 in the BALF was inhibited by Lv-shCD36. The hydroxyproline content of silica+Lv-shCD36 treated groups was significantly lower than in other experimental groups. The degree of fibrosis in the silica+Lv-shCD36-treated groups was less than observed in other experimental groups. The expression of collagen I and III in the silica+Lv-shCD36-treated group was significantly lower than in the other experimental groups.

Conclusion

These results indicate that silencing expression of CD36 can result in the inhibition of L-TGF-β1 activation in a rat silicosis model, thus further preventing the development of silica-induced lung fibrosis.

Pulmonary fibrosis: pathogenesis, etiology and regulation

Pulmonary fibrosis and architectural remodeling of tissues can severely disrupt lung function, often with fatal consequences. The etiology of pulmonary fibrotic diseases is varied, with an array of triggers including allergens, chemicals, radiation and environmental particles. However, the cause of one of the most common pulmonary fibrotic conditions, idiopathic pulmonary fibrosis (IPF), is still unclear. This review examines common mechanisms of pulmonary wound-healing responses following lung injury, and highlights the pathogenesis of some of the most widespread pulmonary fibrotic diseases. A three phase model of wound repair is reviewed that includes; (1) injury; (2) inflammation; and (3) repair. In most pulmonary fibrotic conditions dysregulation at one or more of these phases has been reported. Chronic inflammation can lead to an imbalance in the production of chemokines, cytokines, growth factors, and disrupt cellular recruitment. These changes coupled with excessive pro-fibrotic IL-13 and/or TGFbeta1 production can turn a well-controlled healing response into a pathogenic fibrotic response. Endogenous regulatory mechanisms are discussed including novel areas of therapeutic intervention. Restoring homeostasis to these dysregulated healing responses, or simply neutralizing the key pro-fibrotic mediators may prevent or slow the progression of pulmonary fibrosis.

Potential biomarkers for detecting pulmonary arterial hypertension in patients with systemic sclerosis

Pulmonary arterial hypertension (PAH) is the major complication of systemic sclerosis (SSc) and the main cause of morbi-mortality. It is important to find predictors for this vascular problem. The objective of this study was to determine the serum levels of different biomarkers in patients with SSc and secondary PAH and to compare them with those of healthy control subjects to define their potential role as predictors of PAH. Cross-section study in which 20 patients with SSc were included. PAH was diagnosed by echocardiogram. The optical densities of endoglin (Eng), endothelin-1 (ET-1), platelet-derived growth factor (PDGF), tumoral necrosis factor alpha (TNF-alpha), Transforming growth factor beta 2 (TGF-beta2) and Interleukin 8 (IL-8) were measured in 20 patients with SSc and 20 healthy controls matched by sex. The differences found between the group of patients with PAH and the control group were (mean or median and range): ET-1 (0.20; 0.10-0.35 vs. 0.16; 0.10-0.24; P = 0.0276), IL-8 (195.7; 45.5-504 vs. 118.9; 23-299.5; P = 0.0364), TNF-alpha (0.70; 0.50-0.96 vs. 0.48; 0.38-0.65; P = 1 x 10(-8)) and Eng (0.95; 0.57-1.72 vs. 0.75; 0.57-0.89; P = 0.0028). A correlation was found between the progression of the disease and the development of Raynaud's phenomenon (Rho: 0.67 and P = 0.0011), ET-1 and Eng (Rho: 0.53 and P = 0.0196), and between IL-8 and Eng (Rho: 0.68 and P = 0.0019). In conclusions, the elevation of the serum levels of Eng and ET-1 could represent a useful tool as PAH biomarkers. Nevertheless, the diagnostic value of these markers needs to be determined by prospective studies.

Oxidative stress alters syndecan-1 distribution in lungs with pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease characterized by severe, progressive fibrosis. Roles for inflammation and oxidative stress have recently been demonstrated, but despite advances in understanding the pathogenesis, there are still no effective therapies for IPF. This study investigates how extracellular superoxide dismutase (EC-SOD), a syndecan-binding antioxidant enzyme, inhibits inflammation and lung fibrosis. We hypothesize that EC-SOD protects the lung from oxidant damage by preventing syndecan fragmentation/shedding. Wild-type or EC-SOD-null mice were exposed to an intratracheal instillation of asbestos or bleomycin. Western blot was used to detect syndecans in the bronchoalveolar lavage fluid and lung. Human lung samples (normal and IPF) were also analyzed. Immunohistochemistry for syndecan-1 and EC-SOD was performed on human and mouse lungs. In vitro, alveolar epithelial cells were exposed to oxidative stress and EC-SOD. Cell supernatants were analyzed for shed syndecan-1 by Western blot. Syndecan-1 ectodomain was assessed in wound healing and neutrophil chemotaxis. Increases in human syndecan-1 are detected in lung homogenates and lavage fluid of IPF lungs. Syndecan-1 is also significantly elevated in the lavage fluid of EC-SOD-null mice after asbestos and bleomycin exposure. On IHC, syndecan-1 staining increases within fibrotic areas of human and mouse lungs. In vitro, EC-SOD inhibits oxidant-induced loss of syndecan-1 from A549 cells. Shed and exogenous syndecan-1 ectodomain induce neutrophil chemotaxis, inhibit alveolar epithelial wound healing, and promote fibrogenesis. Oxidative shedding of syndecan-1 is an underlying cause of neutrophil chemotaxis and aberrant wound healing that may contribute to pulmonary fibrosis.

A TSP-1 functional fragment inhibits activation of latent transforming growth factor-beta1 derived from rat alveolar macrophage after bleomycin treatment

The antineoplastic antibiotic, bleomycin, is known to induce a well-recognized model of lung fibrosis. Active transforming growth factor-beta1 (TGF-beta1) plays a key role in lung fibrosis induced by bleomycin, TSP-1 (thrombospondin-1) being critical to the activation of L (latent)-TGF-beta1 by virtue of an association of the TSP-1/L-TGF-beta1 complex with CD36, involving the sequence CSVTCG of the TSP-1 functional fragment. To observe the inhibitory effects of TSP-1 functional fragments, critical for CD36 binding, on the activation of L-TGF-beta1, we isolated alveolar macrophages from Wistar rat lungs 7 days after bleomycin administration (5mg/kg body weight) and cultured the cells with or without TSP-1 functional or control fragments. We observed a cell surface association of TGF-beta1 with CD36 by immunofluorescence and quantified the active and total TGF-beta1 by ELISA. The co-localization of CD36 with TGF-beta1, shown by a yellow fluorescence deriving from a mixture of the green and red of the two components, for the TSP-1 functional fragment groups was clearly less than that of the TSP-1 control fragment groups. The quantities and the percentages of active TGF-beta1 in the TSP-1 functional fragment groups were lower than those in the TSP-1 control fragment groups (P<0.05 or P<0.01). These findings suggest that TSP-1 functional fragments could inhibit the activation of L-TGF-beta1 secreted by activated alveolar macrophages through blocking the binding of TSP-1 to CD36.

A TSP-1 synthetic peptide inhibits bleomycin-induced lung fibrosis in mice

Bleomycin showed toxicity to lung and was recognized to induce a well model of lung fibrosis. Activated alveolar macrophages released increased amounts of transforming growth factor-beta1(TGF-beta1) in response to bleomycin-induced lung injury. Thrombospondin-1(TSP-1) was involved in the activation of latent TGF-beta1(L-TGF-beta1) through the association of the TSP-1/L-TGF-beta1 complex with the cell receptor of TSP-1, CD36. The antagonistic effects of the synthetic peptides were studied by the administration of TSP-1 (447-452) synthetic peptides to the mouse model. The hydroxyproline contents of the TSP-1-treated groups were significantly lower than those of other experimental groups. Inflammation, fibrotic degree and distribution of collagen fibers in the interstitial and alveolar in the TSP-1-treated groups were less than those of the other experimental groups. The expressions of collagen I and III in TSP-1-treated groups were significantly lower than in the other experimental groups. TSP-1 synthetic peptide reduced the tissue fibrotic pathologies and collagen accumulation in the model, resulting in the decreased severity of bleomycin-induced lung injury.

The role of proteoglycans in pulmonary edema development

Pulmonary gas exchange critically depends upon the hydration state and the thinness of the interstitial tissue layer within the alveolo-capillary membrane. In the interstitium, fluid freely moving within the fibrous extracellular matrix (ECM) equilibrates with water chemically bound to hyaluronic acid and proteoglycans (PGs). The dynamic equilibrium between these two phases is set and maintained by the transendothelial fluid and solutes exchanges, by the convective outflows into the lymphatic system, and by the mechanical and hydrophilic properties of the solid elements of the ECM. The fibrous ECM components, in particular the chondroitin sulfate proteoglycan (CS-PG) and the heparan-sulfate proteoglycan (HS-PG) families, play a major role in the maintenance of tissue fluid homeostasis. In fact, they provide: (a) a perivascular and interstitial highly restrictive sieve with respect to plasma proteins, thus modulating both interstitial protein concentration and transendothelial fluid filtration; (b) a mechanical support to lymphatic vessels sustaining and modulating their draining function, and (c) a rigid three-dimensional low-compliant scaffold opposing fluid accumulation into the interstitial space. Fragmentation of PG induced by increased plasma volume, by degradation through proteolytic or inflammatory agents, by exposure to inspiratory gas mixture with modified oxygen fraction, or by increased tissue strain/stress invariably results in the progressive loosening of PG intermolecular bonds with other ECM components. The loss of the PGs regulatory functions compromises the protective role of the tissue solid matrix progressively leading to interstitial and eventually severe lung edema.

Extracellular superoxide dismutase protects against matrix degradation of heparan sulfate in the lung

Asbestosis is a form of interstitial lung disease caused by the inhalation of asbestos fibers, leading to inflammation and pulmonary fibrosis. Inflammation and oxidant/antioxidant imbalances are known to contribute to the disease pathogenesis. Extracellular superoxide dismutase (EC-SOD) is an antioxidant enzyme that has been shown to protect the lung from oxidant-mediated damage, inflammation, and interstitial fibrosis. Extracellular matrix (ECM) components, such as collagen and glycosaminoglycans, are known to be sensitive to oxidative fragmentation. Heparan sulfate, a glycosaminoglycan, is highly abundant in the ECM and tightly binds EC-SOD. We investigated the protective role of EC-SOD by evaluating the interaction of EC-SOD with heparan sulfate in the presence of reactive oxygen species (ROS). We found that ROS-induced heparin and heparan sulfate fragments induced neutrophil chemotaxis across a modified Boyden chamber, which was inhibited by the presence of EC-SOD by scavenging oxygen radicals. Chemotaxis in response to oxidatively fragmented heparin was mediated by Toll-like receptor-4. In vivo, bronchoalveolar lavage fluid from EC-SOD knockout mice at 1, 14, and 28 days after asbestos exposure showed increased heparan sulfate shedding from the lung parenchyma. We demonstrate that one mechanism through which EC-SOD inhibits lung inflammation and fibrosis in asbestosis is by protecting heparin/heparan sulfate from oxidative fragmentation.

The role of versican isoforms V0/V1 in glioma migration mediated by transforming growth factor-beta2

Versican is a large chondroitin sulphate proteoglycan produced by several tumour cell types, including high-grade glioma. The increased expression of certain versican isoforms in the extracellular matrix (ECM) plays a role in tumour cell growth, adhesion and migration. Transforming growth factor-β2 (TGF-β2) is an important modulator of glioma invasion, partially by remodeling the ECM. However, it is unknown whether it interacts with versican during malignant progression of glioma cells. Here, we analysed the effect of TGF-β2 on the expression of versican isoforms. The expression of versican V0/V1 was upregulated by TGF-β2 detected by quantitative polymerase chain reaction and immunoprecipitation, whereas V2 was not induced. Using time-lapse scratch and spheroid migration assays, we observed that the glioma migration rate is significantly increased by exogenous TGF-β2 and inhibited by TGF-β2-specific antisense oligonucleotides. Interestingly, an antibody specific for the DPEAAE region of glycosaminoglycan-β domain of versican was able to reverse the effect of TGF-β2 on glioma migration in a dose-dependent manner. Taken together, we report here that TGF-β2 triggers the malignant phenotype of high-grade gliomas by induction of migration, and that this effect is, at least in part, mediated by versican V0/V1.

Imbalance of Receptor-Regulated and Inhibitory Smads in Lung Fibroblasts from Bleomycin-Exposed Rats

Transforming growth factor (TGF)-beta plays a central role in lung fibrosis, stimulating extracellular matrix deposition. Intracellular signaling of TGF-beta is mediated by Smad proteins. We questioned whether the expression and activation of Smads would be altered in lung fibroblasts from rats exposed to bleomycin, an agent used to provoke an experimental model of lung fibrosis. Fibroblasts were isolated from rat lungs 14 d after intratracheal instillation of bleomycin (BLF) or saline (NLF), and cell cultures established. Whole cell lysates were obtained at baseline, and after stimulation with TGF-beta1 (10 ng/ml). Western blot analysis was performed to measure levels of phosphorylated Smad3 (p-Smad3) and Smad7. Real-time PCR was used to determine changes in Smad7 mRNA after TGF-beta stimulation. We found increased baseline levels of p-Smad3 in BLF versus NLF (P < 0.05). In contrast, baseline levels of Smad7 were comparable. The ratio of stimulatory to inhibitory Smads was increased in BLF compared with NLF (P < 0.05). After stimulation with TGF-beta, levels of p-Smad3 were increased in both groups, with maximal responses at 30 min (P < 0.01). While Smad7 mRNA levels were significantly upregulated (at 1 h) after TGF-beta in both groups, the increase in Smad7 protein was significant in NLF only. We conclude there is sustained activation of Smad signaling in lung fibroblasts isolated from bleomycin-exposed rats, with an imbalance between the levels of p-Smad3 and Smad7. Insufficient levels of the inhibitory Smad7 at baseline, and inadequate response to TGF-beta, may contribute to the fibrotic phenotype characteristic of BLF.

Natural killer T (NKT) cells attenuate bleomycin-induced pulmonary fibrosis by producing interferon-gamma

Pulmonary fibrosis is a progressive illness characterized by interstitial fibrosis. Although the precise mechanism for pulmonary fibrosis is not completely understood, an immune response involving interferon (IFN)-gamma appears to play a role. Therefore, we examined the functional roles of natural killer T (NKT) cells, which produce IFN-gamma and interleukin-4 on activation, in bleomycin-induced pulmonary fibrosis. In NKT cell-deficient mice, pulmonary fibrosis was worse in terms of histology, hydroxyproline levels, and mortality than in control mice. The transforming growth factor (TGF)-beta1 levels were higher in the lung after injecting bleomycin, and blockade of TGF-beta1 by neutralizing monoclonal antibody attenuated the pulmonary fibrosis in CD1d-/- mice. In contrast, the production of IFN-gamma was reduced in lungs from CD1d-/- mice. Moreover, the adoptive transfer of NKT cells into CD1d-/- mice increased IFN-gamma and reduced TGF-beta1 production, attenuating pulmonary fibrosis. An in vitro assay demonstrated that IFN-gamma was involved in suppressing TGF-beta1 production in cells collected from bronchoalveolar lavage. The adoptive transfer of NKT cells from IFN-gamma-/- mice did not reverse pulmonary fibrosis or TGF-beta1 production in lungs of CD1d-/- mice whereas NKT cells from B6 control mice attenuated fibrosis and reduced TGF-beta1 production. In conclusion, IFN-gamma-producing NKT cells play a novel anti-fibrotic role in pulmonary fibrosis by regulating TGF-beta1 production.

Evidence of remodeling in peripheral airways of patients with mild to moderate asthma: effect of hydrofluoroalkane-flunisolide

BACKGROUND

We have shown previously that inflammation in asthma is not restricted to central airways but can also be demonstrated in peripheral airways. It is not clear whether inflammation of the peripheral airways is associated with structural changes and whether this remodeling process can be modulated by deposition of inhaled corticosteroids (ICSs).

OBJECTIVES

To compare remodeling in peripheral and central airways and to investigate the effects of hydrofluoroalkane (HFA)-ICS on remodeling at these sites.

METHODS

Transbronchial and endobronchial biopsies were obtained from 12 patients with mild to moderate asthma before and after a 6-week course of HFA-ICS (flunisolide). Total collagen deposition, expression of collagen III, TGF-beta, and alpha-smooth muscle actin were examined by using Van Gieson staining and immunocytochemistry, respectively.

RESULTS

Total collagen occupied 37.7% of the wall area of peripheral airways, compared with 54.5% of the wall area of central airways (P = .04). There was no significant difference in central versus peripheral airways for collagen III or alpha-smooth muscle actin immunoreactivity and in the number of TGF-beta(+) cells in the submucosa. The only significant effect of HFA-flunisolide was a decrease in alpha-smooth muscle actin area in peripheral airways (13.4% vs 4.6%; P = .01) that correlated with the percentage increase in forced expiratory flow at 25% to 75% of vital capacity (r(s) = -1.00; P = .00).

CONCLUSION

Our data show that there is a considerable degree of airway remodeling in peripheral airways in patients with asthma and confirm the inability of ICS to modulate collagen deposition and TGF-beta expression. Treatment with HFA-flunisolide is associated with a significant decrease in the expression of alpha-smooth muscle actin in peripheral airways, which correlated with improvement in peripheral airway function.

Interferon Gamma-1b in the Treatment of Idiopathic Pulmonary Fibrosis

Objective:

To examine the clinical aspects of idiopathic pulmonary fibrosis (IPF) and the efficacy and safety of interferon gamma-1b (IFNγ−1b) in its treatment.

Data Sources:

Epidemiologic, preclinical, and clinical studies published in the English language were identified by a MEDLINE search (1966–January 2005) using the search terms idiopathic pulmonary fibrosis, cryptogenic fibrosing alveolitis, and interferon. Additional citations were identified from the reference lists of related publications.

Study Selection and Data Extraction:

Selected preclinical studies describing the pathophysiologic basis for IFNγ−1b therapy and all clinical studies were included. Additional trials describing other treatment modalities and the determinants of response to therapy in patients with IPF were also reviewed.

Data Synthesis:

IFNγ−1b targets the fibrotic rather than inflammatory processes of IPF. The efficacy of IFNγ−1b in patients with IPF is inconsistent with regard to changes in pulmonary function and mortality, although a modest survival benefit was observed in the largest clinical trial. Adverse events related to IFNγ−1b are frequent although transient. Several cases of respiratory failure occurring subsequent to the administration of IFNγ−1b are documented.

CONCLUSIONS:

To date, although trials suggest that earlier-stage IPF may be responsive to IFNγ−1b, study results overall are inconsistent; further investigation is needed.

Altered production and proteolytic processing of brevican by transforming growth factor beta in cultured astrocytes

Brevican, a proteoglycan of the lectican family, inhibits neurite outgrowth and may also stabilize synapses. Little is known about its expression or function in vitro. This study seeks to determine whether a brevican-containing matrix is present in neural cultures, and if so, how the production of brevican may be modulated. To accomplish this, the content of brevican and its proteolytic fragments were measured in primary cultures of neurons, astrocytes and microglia after treatment with cytokines. These experiments revealed that astrocytes and neurons express several isoforms of brevican, whereas microglia do not produce this proteoglycan. Cleavage fragments of brevican were found primarily in neuronal and astrocyte culture medium. ADAMTS4 (a disintegrin and metalloproteinase with thrombospondin motifs), a protease that selectively cleaves lecticans, was detected in cultures of neurons, astrocytes and microglia. When astrocytes were challenged with various cytokines, it was found that treatment with transforming growth factor beta (TGFbeta) resulted in a marked increase in intact brevican in the culture medium that was accompanied by a trend for a decrease in ADAMTS-generated fragments of brevican and apparent ADAMTS activity. Thus, TGFbeta may play a role in neuronal plasticity through its regulation of brevican and the activity of the ADAMTSs.

Antifibrotic effect of interferon gamma in silicosis model of rat

This study presents the antifibrotic effect of interferon gamma (IFN-gamma) in silicosis of rats. Wistar rats were received saline or 20 mg of quartz by intratracheal instillation. The next day after instillation, silicosis model of rats were daily treated IFN-gamma (1.0 x 10(5) units/rat) or saline by intramuscular route. At 1 month or 2 months after instillation, rats were sacrificed to determine hydroxyproline content and observe the change of fibrosis and expression of interleukin-4 (IL-4) and transforming growth factor-beta1 (TGF-beta1) in the lung of rats. The hydroxyproline content of IFN-gamma treated groups was significantly lower than that of quartz groups (P<0.05). At 1 month after instillation, there were Stage II and II+ of silicotic nodules in quartz group; however, in IFN-gamma treated group only cellular nodules (Stage I) were observed. At 2 months after instillation, there was Stage II+ and III of silicotic nodules in quartz group. In IFN-gamma treated group Stage II was found. The expressions of IL-4 (2.19+/-0.90, 0.61+/-0.22, respectively) and TGF-beta1 (1.37+/-0.31, 1.76+/-0.72, respectively) in IFN-gamma treated groups were significantly lower than those in quartz groups (IL-4: 3.33+/-1.27, 1.99+/-0.80; TGF-beta1: 3.67+/-0.63, 4.90+/-1.11, respectively; P<0.05 or P<0.01). It may be concluded that the decreased expression of IL-4 and TGF-beta1 may be associated with decreased hydroxyproline synthesis, which then results in decreased lung fibrosis.

Alterations in lung mechanics in decorin-deficient mice

Decorin, a small leucine-rich proteoglycan with a widespread tissue distribution, is required for the normal fibrillogenesis of collagen in most tissues. Because collagen is important in determining the elastic behavior of the lung, we hypothesized that lung tissue mechanics would be altered in a mutant mouse in which the single decorin gene was abrogated by targeted deletion ( Dcn−/−). Complex impedance of the respiratory system was measured in C57Bl/6 mice ( Dcn−/− and Dcn+/+) using a small animal ventilator that delivers a volume signal with multiple frequencies to the trachea. A constant-phase model was fit to calculate airway resistance (Raw), tissue damping, and tissue elastance. Compliance of the respiratory system (Crs) was measured from a pressure volume curve during stepwise deflations. Lungs were excised, and parenchymal tissue strips were mounted in an organ bath for in vitro measurement of tissue impedance and quasistatic length-stress curves. In addition, pulmonary tissue was examined by immunohistochemistry and immunoblotting. In vivo, in the Dcn−/− mice, Raw was decreased and Crs was increased. Similarly, in vitro, length-stress curves showed increased compliance of the strips in the Dcn−/− mice. These alterations in lung tissue mechanical behavior in Dcn−/− mice support a critical role for decorin in the formation of the lung collagen network.

Changes in Smad expression and subcellular localization in bleomycin-induced pulmonary fibrosis

Administration of bleomycin (BM) produces inflammation and fibrosis of the lung in humans and experimental animals. The molecular defects by which BM induces these pathological effects have not been studied in detail. We studied the expression of Smad family proteins, key molecules involved in mediating transforming growth factor (TGF)-β signaling from the cell membrane to the nucleus, during the early and late phases of BM-induced fibrogenesis. Pulmonary fibrosis was induced in male Sprague-Dawley rats by a single intratracheal injection (1.5 units) of BM. Control rats received saline. Rats were killed at 3, 5, 7, 14, and 28 days after BM, cytosolic and nuclear proteins were extracted and isolated from lung tissues, and Smad proteins were probed with specific antibodies. In BM-exposed lung tissue, compared with control, Smad3 decreased persistently in the cytosol and increased transiently in the nucleus. There was a persistent increase in phosphorylation and nuclear accumulation of Smad2/3. Smad4 was increased transiently in both the cytosol and nucleus. A significant and progressive decrease in the expression of Smad7, the endogenous inhibitor of TGF-β/Smad signaling, was observed after BM instillation. Collectively, our results indicate that an imbalance between agonistic Smads2–4 and antagonistic Smad7 may result in the unchecked activation of an autocrine TGF-β loop, which contributes to the pathogenesis of BM-induced pulmonary fibrosis.

Mechanical strain enhances proteoglycan message in fibroblasts from asthmatic subjects

BACKGROUND

Remodelling of the asthmatic airway includes increased deposition of proteoglycan (PG) molecules. One of the stimuli driving airway remodelling may be excessive mechanical stimulation.

OBJECTIVE

We hypothesized that fibroblasts from asthmatic patients would respond to excessive mechanical strain with up-regulation of message for PGs.

METHODS

We obtained fibroblasts from asthmatic patients (AF) and normal volunteers (NF) using endobronchial biopsy. Cells were maintained in culture until the fifth passage and then grown on a flexible collagen-coated membrane. Using the Flexercell device, cells were then subjected to cyclic stretch at 30% amplitude at 1 Hz for 24 h. Control cells were unstrained. Total RNA was extracted from the cell layer and quantitative RT-PCR performed for decorin, lumican and versican mRNA.

RESULTS

In unstrained cells, the expression of decorin mRNA was greater in AF than NF. With strain, NF showed increased expression of versican mRNA and AF showed increased expression of versican and decorin mRNA. The relative increase in versican mRNA expression with strain was greater in AF than NF.

CONCLUSIONS

These data support the hypothesis that proteoglycan message is increased in asthmatic fibroblasts subject to mechanical strain. This finding has implications for the mechanisms governing airway wall remodelling in asthma.

Presence of activated mobile fibroblasts in bronchoalveolar lavage from patients with mild asthma

Activated fibroblasts are suggested to be involved in the deposition of extracellular matrix in the formation of peribronchial fibrosis in asthma. We report the novel finding of activated elongated fibroblasts accompanied by elevated numbers of eosinophils in bronchoalveolar lavage fluid from 5 out of 12 patients with mild asthma (= 42%), whereas no fibroblasts were observed in the control subjects without asthma (n = 17). The elongated fibroblasts migrated twice as far when compared with fibroblasts from corresponding bronchial biopsies from the same patients, accompanied by an induced expression of RhoA and Rac1, indicating that the increased expression of these proteins are linked to increased migratory capabilities. Moreover, the elongated fibroblasts had an elevated production of the proteoglycans biglycan, versican, perlecan, and decorin, which correlated to an active cytoplasm in these cells. Differential expression patterns between the two fibroblast groups in motility-regulating proteins, such as cofilin, nuclear chloride ion channel protein, and heat-shock protein 20, were identified by two-dimensional electrophoresis and mass spectrometry. These findings indicate the presence of activated and mobile fibroblasts accompanied by an induced inflammatory response outside the airway epithelium in patients with mild asthma, results that may play a role in formation of airway fibrosis.

Col1a2 enhancer regulates collagen activity during development and in adult tissue repair

An enhancer region in the type I collagen alpha 2 chain (pro-Col1a2) promoter has been previously identified approximately -17 kb away from the transcription start site. This upstream region termed the far-upstream-enhancer contains three DNAse I hypersensitive sites and has been shown to be conserved between mouse and human genes. In this study, we used transgenic mice harbouring the complete promotor sequence of the pro-Col1a2 gene up to -17 kb to examine the role of this enhancer in the expression and regulation of the collagen gene during development and in adult tissues pre and post injury. By careful histological mapping of the collagen type I endogenous gene distribution with that of the transgene driven by the mouse far upstream enhancer, we are able to show that in early days of collagen expression, E8.5-9.5, the endogenous gene preceded transgene expression. However, by E11.5 the overall pattern becomes synchronous with a few exceptions. In adult tissue, both endogenous and transgene expression are attenuated and both are reactivated in parallel in various organs by physical injury or fibrogenic cytokine injection. These findings suggest that the enhancer is central to the activation of the collagen type I and that mice harbouring this enhancer/reporter provide a useful model to follow collagen gene transcription activity and for investigating cellular activity in tissue fibrosis.

Keratocyte phenotype mediates proteoglycan structure: a role for fibroblasts in corneal fibrosis

In pathological corneas, accumulation of fibrotic extracellular matrix is characterized by proteoglycans with altered glycosaminoglycans that contribute to the reduced transparency of scarred tissue. During wound healing, keratocytes in the corneal stroma transdifferentiate into fibroblasts and myofibroblasts. In this study, molecular markers were developed to identify keratocyte, fibroblast, and myofibroblast phenotypes in primary cultures of corneal stromal cells and the structure of glycosaminoglycans secreted by these cells was characterized. Quiescent primary keratocytes expressed abundant protein and mRNA for keratocan and aldehyde dehydrogenase class 3 and secreted proteoglycans containing macromolecular keratan sulfate. Expression of these marker compounds was reduced in fibroblasts and also in transforming growth factor-beta-induced myofibroblasts, which expressed high levels of alpha-smooth muscle actin, biglycan, and the extra domain A (EDA or EIIIA) form of cellular fibronectin. Collagen types I and III mRNAs were elevated in both fibroblasts and in myofibroblasts. Expression of these molecular markers clearly distinguishes the phenotypic states of stromal cells in vitro. Glycosaminoglycans secreted by fibroblasts and myofibroblasts were qualitatively similar to and differed from those of keratocytes. Chondroitin/dermatan sulfate abundance, chain length, and sulfation were increased as keratocytes became fibroblasts and myofibroblasts. Fluorophore-assisted carbohydrate electrophoresis analysis demonstrated increased N-acetylgalactosamine sulfation at both 4- and 6-carbons. Hyaluronan, absent in keratocytes, was secreted by fibroblasts and myofibroblasts. Keratan sulfate biosynthesis, chain length, and sulfation were significantly reduced in both fibroblasts and myofibroblasts. The qualitatively similar expression of glycosaminoglycans shared by fibroblasts and myofibroblasts suggests a role for fibroblasts in deposition of non-transparent fibrotic tissue in pathological corneas.

The role of chemokines in the pathogenesis of scleroderma

PURPOSE OF REVIEW

The triad of pathologic changes that defines systemic sclerosis (scleroderma) includes immune system activation with autoimmunity; an obliterative, proliferative small vessel vasculopathy; and fibrosis. Available data suggest that several cytokines, including chemokines, contribute to the development of scleroderma complications. This review focuses on chemokines and their contribution to tissue fibrosis and pulmonary hypertension in scleroderma.

RECENT FINDINGS

Proteins and mRNAs for monocyte chemoattractant protein-1; pulmonary and activation-regulated chemokine; macrophage inflammatory protein-1, regulated upon activation normal T cell expressed and secreted; interleukin-8; and transforming growth factor-beta have been found in increased amounts in blood or involved tissue from scleroderma patients. These factors are likely to contribute directly to tissue damage in scleroderma through several pathways, including stimulation of extracellular matrix production, induction of TGF-beta production and activation, and chemoattraction of T cells and nonspecific inflammatory cells into tissues.

SUMMARY

Multiple chemokines are part of the pathologic network that causes tissue damage in scleroderma, and, as such, may provide therapeutic targets in scleroderma.

Injury and repair in lung and airways

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common causes of morbidity and mortality in the intensive care unit. ALI/ARDS occurs as a result of systemic inflammation, usually triggered by a microorganism. Activation of leukocytes and release of proinflammatory mediators from multiple cellular sources result in both local and distant tissue injury. Tumor necrosis factor-alpha and interleukin-1 beta are the best characterized of the proinflammatory cytokines contributing to ALI/ARDS and subsequent fibrosis. The ultimate clinical course of ALI/ARDS often is determined by the ability of the injured lung to repopulate the alveolar epithelium with functional cells. Death may occur when fibrosis predominates the healing response, as it results in worsening lung compliance and oxygenation. The rodent bleomycin model of lung fibrosis allows the use of molecular tools to dissect the cellular and subcellular processes leading to fibrosis. The elements of this response may provide therapeutic targets for the prevention of this devastating complication of ALI/ARDS.