Production of fibronectin by the human alveolar macrophage: mechanism for the recruitment of fibroblasts to sites of tissue injury in interstitial lung diseases

ALOX15+ M2 macrophages contribute to epithelial remodeling in eosinophilic chronic rhinosinusitis with nasal polyps

BACKGROUND

Epithelial remodeling is a prominent feature of eosinophilic chronic rhinosinusitis with nasal polyps (eCRSwNP), and infiltration of M2 macrophages plays a pivotal role in the pathogenesis of eCRSwNP, but the underlying mechanisms remain undefined.

OBJECTIVE

We sought to investigate the role of ALOX15+ M2 macrophages in the epithelial remodeling of eCRSwNP.

METHODS

Digital spatial transcriptomics and single-cell sequencing analyses were used to characterize the epithelial remodeling and cellular infiltrate in eCRSwNP. Hematoxylin and eosin staining, immunohistochemical staining, and immunofluorescence staining were used to explore the relationship between ALOX15+ M2 (CD68+CD163+) macrophages and epithelial remodeling. A coculture system of primary human nasal epithelial cells (hNECs) and the macrophage cell line THP-1 was used to determine the underlying mechanisms.

RESULTS

Spatial transcriptomics analysis showed the upregulation of epithelial remodeling-related genes, such as Vimentin and matrix metalloproteinase 10, and enrichment of epithelial-mesenchymal transition (EMT)-related pathways, in the epithelial areas in eCRSwNP, with more abundance of epithelial basal, goblet, and glandular cells. Single-cell analysis identified that ALOX15+, rather than ALOX15-, M2 macrophages were specifically highly expressed in eCRSwNP. CRSwNP with high ALOX15+ M2THP-1-IL-4+IL-13 macrophages had more obvious epithelial remodeling features and increased genes associated with epithelial remodeling and integrity of epithelial morphology versus that with low ALOX15+ M2THP-1-IL-4+IL-13 macrophages. IL-4/IL-13-polarized M2THP-1-IL-4+IL-13 macrophages upregulated expressions of EMT-related genes in hNECs, including Vimentin, TWIST1, Snail, and ZEB1. ALOX15 inhibition in M2THP-1-IL-4+IL-13 macrophages resulted in reduction of the EMT-related transcripts in hNECs. Blocking chemokine (C-C motif) ligand 13 signaling inhibited M2THP-1-IL-4+IL-13 macrophage-induced EMT alteration in hNECs.

CONCLUSIONS

ALOX15+ M2 macrophages are specifically increased in eCRSwNP and may contribute to the pathogenesis of epithelial remodeling via production of chemokine (C-C motif) ligand 13.

Osteopontin and fibronectin in lung tissue, serum, and bronchoalveolar lavage fluid of dogs with idiopathic pulmonary fibrosis and control dogs

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) affects West Highland white terriers (WHWTs). Osteopontin (SPP1) and fibronectin (FN1) are associated with human IPF and are overexpressed by bronchoalveolar lavage fluid (BALF) macrophages in dogs with IPF.

OBJECTIVE

To investigate the value of these proteins as biomarkers of IPF.

ANIMALS

West Highland white terriers (WHWTs) with IPF, control WHWTs, and terriers.

METHODS

Cross-sectional observational study. Immunohistochemistry was used to localize SPP1 and FN1 in lung tissue. Serum and BALF SPP1 and FN1 concentrations were measured using canine ELISA kits and compared between groups.

RESULTS

Osteopontin stained ciliated epithelial cells, smooth muscular cells, and macrophages of all included dogs, and type-II pneumocytes and extracellular matrix of all 12 diseased WHWTs, 4/6 control WHWTs, and none of the 3 terriers. Osteopontin serum concentration was higher in diseased WHWTs (n = 22; 2.15 ng/mL [0.74-5.30]) compared with control WHWTs (n = 13; 0.63 ng/mL [0.41-1.63]; P = .005) and terriers (n = 15; 0.31 ng/mL [0.19-0.51]; P < .0001), and in control WHWTs compared with terriers (P = .005). Osteopontin BALF concentrations were higher in diseased (0.27 ng/mL [0.14-0.43]) and control WHWTs (0.25 ng/mL [0.14-0.40]), compared with terriers (0.02 ng/mL [0.01-0.08]; P < .0001 and P = .003, respectively). Fibronectin (FN1) serum concentrations were lower in diseased dogs (1.03 ng/mL [0.35-1.48]) and control WHWTs (0.61 ng/mL [0.24-0.65]) compared with terriers (2.72 ng/mL [0.15-5.21]; P < .0001 and P = .0001, respectively). There was no difference in FN1 immunostaining and FN1 BALF concentrations between groups.

CONCLUSIONS

Results suggest that SPP1 is involved in pathogenesis of IPF and could predispose that breed to the disease. Osteopontin serum concentration could serve as a diagnostic biomarker of IPF.

Targeting pathogenic macrophages by the application of SHP-1 agonists reduces inflammation and alleviates pulmonary fibrosis

Idiopathic pulmonary fibrosis is a progressive fibrotic disorder with no cure that is characterized by deterioration of lung function. Current FDA-approved drugs for IPF delay the decline in lung function, but neither reverse fibrosis nor significantly improve overall survival. SHP-1 deficiency results in hyperactive alveolar macrophages accumulating in the lung, which contribute to the induction of pulmonary fibrosis. Herein, we investigated whether employing a SHP-1 agonist ameliorates pulmonary fibrosis in a bleomycin-induced pulmonary fibrosis murine model. Histological examination and micro-computed tomography images showed that SHP-1 agonist treatment alleviates bleomycin-induced pulmonary fibrosis. Reduced alveolar hemorrhage, lung inflammation, and collagen deposition, as well as enhanced alveolar space, lung capacity, and improved overall survival were observed in mice administered the SHP-1 agonist. The percentage of macrophages collected from bronchoalveolar lavage fluid and circulating monocytes in bleomycin-instilled mice were also significantly reduced by SHP-1 agonist treatment, suggesting that the SHP-1 agonist may alleviate pulmonary fibrosis by targeting macrophages and reshaping the immunofibrotic niche. In human monocyte-derived macrophages, SHP-1 agonist treatment downregulated CSF1R expression and inactivated STAT3/NFκB signaling, culminating in inhibited macrophage survival and perturbed macrophage polarization. The expression of pro-fibrotic markers (e.g., MRC1, CD200R1, and FN1) by IL4/IL13-induced M2 macrophages that rely on CSF1R signaling for their fate-determination was restricted by SHP-1 agonist treatment. While M2-derived medium promoted the expression of fibroblast-to-myofibroblast transition markers (e.g., ACTA2 and COL3A1), the application of SHP-1 agonist reversed the transition in a dose-dependent manner. Our report indicates that pharmacological activation of SHP-1 ameliorates pulmonary fibrosis via suppression of CSF1R signaling in macrophages, reduction of pathogenic macrophages, and the inhibition of fibroblast-to-myofibroblast transition. Our study thus identifies SHP-1 as a druggable target for the treatment of IPF, and suggests that the SHP-1 agonist may be developed as an anti-pulmonary fibrosis medication that both suppresses inflammation and restrains fibroblast-to-myofibroblast transition.

Remarkable sex-specific differences at single-cell resolution in neonatal hyperoxic lung injury

Exposure to supraphysiological concentrations of oxygen (hyperoxia) predisposes to bronchopulmonary dysplasia (BPD), which is characterized by abnormal alveolarization and pulmonary vascular development, in preterm neonates. Neonatal hyperoxia exposure is used to recapitulate the phenotype of human BPD in murine models. Male sex is considered an independent predictor for the development of BPD, but the main mechanisms underlying sexually dimorphic outcomes are unknown. Our objective was to investigate sex-specific and cell-type specific transcriptional changes that drive injury in the neonatal lung exposed to hyperoxia at single-cell resolution and delineate the changes in cell-cell communication networks in the developing lung. We used single-cell RNA sequencing (scRNAseq) to generate transcriptional profiles of >35,000 cells isolated from the lungs of neonatal male and female C57BL/6 mice exposed to 95% [Formula: see text] between PND1-5 (saccular stage of lung development) or normoxia and euthanized at PND7 (alveolar stage of lung development). ScRNAseq identified 22 cell clusters with distinct populations of endothelial, epithelial, mesenchymal, and immune cells. Our data identified that the distal lung vascular endothelium (composed of aerocytes and general capillary endothelial cells) is exquisitely sensitive to hyperoxia exposure with the emergence of an intermediate capillary endothelial population with both general capillaries (gCap) and aerocytes or alveolar capillaries (aCap) markers. We also identified a myeloid-derived suppressor cell population from the lung neutrophils. Sex-specific differences were evident in all lung cell subpopulations but were striking among the lung immune cells. Finally, we identified that the specific intercellular communication networks and the ligand-receptor pairs that are impacted by neonatal hyperoxia exposure.

Tissue mechanics coevolves with fibrillar matrisomes in healthy and fibrotic tissues

Fibrillar proteins are principal components of extracellular matrix (ECM) that confer mechanical properties to tissues. Fibrosis can result from wound repair in nearly every tissue in adults, and it associates with increased ECM density and crosslinking as well as increased tissue stiffness. Such fibrotic tissues are a major biomedical challenge, and an emerging view posits that the altered mechanical environment supports both synthetic and contractile myofibroblasts in a state of persistent activation. Here, we review the matrisome in several fibrotic diseases, as well as normal tissues, with a focus on physicochemical properties. Stiffness generally increases with the abundance of fibrillar collagens, the major constituent of ECM, with similar mathematical trends for fibrosis as well as adult tissues from soft brain to stiff bone and heart development. Changes in expression of other core matrisome and matrisome-associated proteins or proteoglycans contribute to tissue stiffening in fibrosis by organizing collagen, crosslinking ECM, and facilitating adhesion of myofibroblasts. Understanding how ECM composition and mechanics coevolve during fibrosis can lead to better models and help with antifibrotic therapies.

Interstitial pneumonia and diffuse alveolar damage in domestic animals

Classification of pneumonia in animals has been controversial, and the most problematic pattern is interstitial pneumonia. This is true from the gross and histologic perspectives, and also from a mechanistic point of view. Multiple infectious and noninfectious diseases are associated with interstitial pneumonia, all of them converging in the release of inflammatory mediators that generate local damage and attract inflammatory cells that inevitably trigger a second wave of damage. Diffuse alveolar damage is one of the more frequently identified histologic types of interstitial pneumonia and involves injury to alveolar epithelial and/or endothelial cells, with 3 distinct stages. The first is the “exudative” stage, with alveolar edema and hyaline membranes. The second is the “proliferative” stage, with hyperplasia and reactive atypia of type II pneumocytes, infiltration of lymphocytes, plasma cells, and macrophages in the interstitium and early proliferation of fibroblasts. These stages are reversible and often nonfatal. If damage persists, there is a third “fibrosing” stage, characterized by fibrosis of the interstitium due to proliferation of fibroblasts/myofibroblasts, persistence of type II pneumocytes, segments of squamous metaplasia of alveolar epithelium, plus inflammation. Understanding the lesion patterns associated with interstitial pneumonias, their causes, and the underlying mechanisms aid in accurate diagnosis that involves an interdisciplinary collaborative approach involving pathologists, clinicians, and radiologists.

Early skeletal muscle pathology and disease progress in the dy3K/dy3K mouse model of congenital muscular dystrophy with laminin α2 chain-deficiency

Deficiency of laminin α2 chain leads to a severe form of congenital muscular dystrophy (LAMA2-CMD), and dystrophic symptoms progress rapidly in early childhood. Currently, there is no treatment for this detrimental disorder. Development of therapies is largely hindered by lack of understanding of mechanisms involved in the disease initiation and progress, both in patients but also in mouse models that are commonly used in the preclinical setup. Here, we unveil the first pathogenic events and characterise the disease development in a mouse model for LAMA2-CMD (dy^3K/dy^3K), by analysing muscles at perinatal, neonatal and postnatal stages. We found that apoptotic muscle fibres were present as early as postnatal day 1. Other typical dystrophic hallmarks (muscle degeneration, inflammation, and extensive production of the extracellular matrix proteins) were clearly evident already at postnatal day 4, and the highest degree of muscle deterioration was reached by day 7. Interestingly, the severe phenotype of limb muscles partially recovered on days 14 and 21, despite worsening of the general condition of the dy^3K/dy^3K mouse by that age. We found that masticatory muscles were severely affected in dy^3K/dy^3K mice and this may be an underlying cause of their malnutrition, which contributes to death around day 21. We also showed that several signalling pathways were affected already in 1-day-old dy^3K/dy^3K muscle. Therapeutic tests in the dy^3K/dy^3K mouse model should therefore be initiated shortly after birth, but should also take into account timing and correlation between regenerative and pathogenic events.

Sinonasal and Laryngeal Sarcoidosis-An Uncommon Presentation and Management Challenge

Sarcoidosis is a chronic inflammatory disease of uncertain etiology characterized by the formation of noncaseating granulomas. The thorax is involved in 95% of cases, but any organ can be involved. Sinonasal or laryngeal involvement is uncommon and can be difficult to diagnose. The reported incidence of sarcoidosis in the upper airway clearly depends on study characteristics, and this creates uncertainty about the actual incidence. In a large prospective study in the United States, upper respiratory tract involvement occurred in 3% of the patients. Some patients have upper airway involvement without thoracic disease, and this presentation may cause delays in diagnosis. These patients have nonspecific symptoms which range from minimal nasal stuffiness to life-threatening upper airway obstruction. Currently, there is no established standard therapy for the management of upper airway sarcoidosis. These patients often respond poorly to nasal and/or inhaled corticosteroids and require long courses of oral corticosteroids. Patients with poor responses to oral corticosteroids or severe side effects may respond to tumor necrosis factor alpha inhibitors. In this review, we will discuss the clinical presentation, pathogenesis, diagnostic tests, drug treatment, surgical management options and the challenges clinicians have managing these patients.

Radiation-induced lung injury: impact on macrophage dysregulation and lipid alteration - a review

Lung cancer continues to be the leading cause of cancer deaths and more than one million lung cancer patients will die every year worldwide. Radiotherapy (RT) plays an important role in lung cancer treatment, but the side effects of RT are pneumonitis and pulmonary fibrosis. RT-induced lung injury causes damage to alveolar-epithelial cells and vascular endothelial cells. Macrophages play an important role in the development of pulmonary fibrosis despite its role in immune response. These injury activated macrophages develop into classically activated M1 macrophage or alternative activated M2 macrophage. It secretes cytokines, interleukins, interferons, and nitric oxide. Several pro-inflammatory lipids and pro-apoptotic proteins cause lipotoxicity such as LDL, FC, DAG, and FFA. The overall findings in this review conclude the importance of macrophages in inducing toxic/inflammatory effects during RT of lung cancer, which is clinically vital to treat the radiation-induced fibrosis.

Overexpression of OSM and IL-6 impacts the polarization of pro-fibrotic macrophages and the development of bleomycin-induced lung fibrosis

Although recent evidence indicates that gp130 cytokines, Oncostatin M (OSM) and IL-6 are involved in alternative programming of macrophages, their role in lung fibrogenesis is poorly understood. Here, we investigated the effect of transient adenoviral overexpression of OSM or IL-6 in mice during bleomycin-induced lung fibrosis. Lung fibrosis and M2-like macrophage accumulation were assessed by immunohistochemistry, western blotting, gene expression and flow cytometry. Ex-vivo isolated alveolar and bone marrow-derived macrophages were examined for M2-like programming and signalling. Airway physiology measurements at day 21 demonstrated that overexpression of OSM or IL-6 exacerbated bleomycin-induced lung elastance, consistent with histopathological assessment of extracellular matrix and myofibroblast accumulation. Flow cytometry analysis at day 7 showed increased numbers of M2-like macrophages in lungs of mice exposed to bleomycin and OSM or IL-6. These macrophages expressed the IL-6Rα, but were deficient for OSMRβ, suggesting that IL-6, but not OSM, may directly induce alternative macrophage activation. In conclusion, the gp130 cytokines IL-6 and OSM contribute to the accumulation of profibrotic macrophages and enhancement of bleomycin-induced lung fibrosis. This study suggests that therapeutic strategies targeting these cytokines or their receptors may be beneficial to prevent the accumulation of M2-like macrophages and the progression of fibrotic lung disease.

Fucoxanthin inhibits profibrotic protein expression in vitro and attenuates bleomycin-induced lung fibrosis in vivo

Pulmonary fibrosis, a potentially fatal disease, results from acute and chronic interstitial lung diseases. Fucoxanthin (Fx), a carotenoid found in brown seaweed, shows a wide range of pharmacological activities. In this study, we investigated the antifibrotic effects of fucoxanthin and their underlying molecular mechanisms in transforming growth factor-beta1 (TGF-β1)-stimulated human pulmonary fibroblasts (HPFs). Thus, the effects of Fx on TGF-β1-induced expression of fibrotic factors, such as alpha-smooth muscle actin (α-SMA), type 1 collagen, fibronectin, and interleukin-6 (IL-6), in HPFs were investigated. We performed an enzyme-linked immunosorbent assay (ELISA), and a western blot analysis to elucidate the mechanisms underlying the antifibrotic effects of Fx in TGF-β1-stimulated cells. The contractile activity of HPFs was measured using a collagen gel contraction assay. We also investigated the effects of Fx on inflammation and fibrosis in bleomycin (BLM)-induced pulmonary fibrosis mouse model. We observed that Fx inhibited the TGF-β1-induced expression of α-SMA, type 1 collagen, fibronectin, and IL-6 in HPFs. Similarly, markedly inhibition of TGF-β1-induced phosphorylation of p-38 mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K)/Akt, and Smad2/Smad3 (Smad2/3) was observed after Fx treatment. Collagen contraction also significantly decreased on fucoxanthin treatment. Intraperitoneal injection of Fx (10mg/kg) in mice inhibited BLM-induced lung fibrosis and type I collagen protein expression. Overall, our findings suggest that Fx may be effective in the treatment of pulmonary fibrosis owing to its potent antifibrotic activity.

Human Lung Mononuclear Phagocytes in Health and Disease

The lungs are vulnerable to attack by respiratory insults such as toxins, allergens, and pathogens, given their continuous exposure to the air we breathe. Our immune system has evolved to provide protection against an array of potential threats without causing collateral damage to the lung tissue. In order to swiftly detect invading pathogens, monocytes, macrophages, and dendritic cells (DCs)-together termed mononuclear phagocytes (MNPs)-line the respiratory tract with the key task of surveying the lung microenvironment in order to discriminate between harmless and harmful antigens and initiate immune responses when necessary. Each cell type excels at specific tasks: monocytes produce large amounts of cytokines, macrophages are highly phagocytic, whereas DCs excel at activating naïve T cells. Extensive studies in murine models have established a division of labor between the different populations of MNPs at steady state and during infection or inflammation. However, a translation of important findings in mice is only beginning to be explored in humans, given the challenge of working with rare cells in inaccessible human tissues. Important progress has been made in recent years on the phenotype and function of human lung MNPs. In addition to a substantial population of alveolar macrophages, three subsets of DCs have been identified in the human airways at steady state. More recently, monocyte-derived cells have also been described in healthy human lungs. Depending on the source of samples, such as lung tissue resections or bronchoalveolar lavage, the specific subsets of MNPs recovered may differ. This review provides an update on existing studies investigating human respiratory MNP populations during health and disease. Often, inflammatory MNPs are found to accumulate in the lungs of patients with pulmonary conditions. In respiratory infections or inflammatory diseases, this may contribute to disease severity, but in cancer patients this may improve clinical outcomes. By expanding on this knowledge, specific lung MNPs may be targeted or modulated in order to attain favorable responses that can improve preventive or treatment strategies against respiratory infections, lung cancer, or lung inflammatory diseases.

Inflammasome activators induce fibronectin expression and release in macrophages

Extracellular fibronectin (Fn) can activate pro-inflammatory pathways and serves as an endogenous danger signalling molecule; thus, it has been suggested as a biomarker for several diseases. In the present study, we found that pathogen-derived activators of the inflammasomes induce the expression and secretion of Fn in macrophages through a mechanism involving adenosine triphosphate and caspase-1 activation. We also found that plasma Fn induces caspase-1 activation and cell death in macrophages, epithelial cells, and fibroblasts. Together, these results indicate that Fn plays a critical role in inflammasome-activated cells by amplifying caspase-1 activation and inducing inflammatory cell death.

Bioglass promotes wound healing through modulating the paracrine effects between macrophages and repairing cells

Bioglass stimulates macrophages to switch to the M2 phenotype and modulates the paracrine effects between macrophages and repairing cells.

Drug-Induced Lung Toxicity

The number of blood-borne chemotherapeutic agents implicated in drug-induced lung toxicity continues to increase, although problems in detection remain. The initiation of drug-induced lung injury can have an immunologic or nonimmunologic basis. If endothelial cells are injured, interstitial pulmonary edema may result. Regardless of the source of injury, the progression of drug-induced lung toxicity is often quite similar, involving (1) parenchymal damage, (2) recruitment of inflammatory cells, and (3) progression of the inflammatory process. If the inflammatory reponse is sufficiently severe and disperse, increased collagen can be deposited in interstitial and intra-alveolar areas. The resulting attenuation of gas exchange can induce dyspnea and possibly death. Recent research suggests mediation of the fibrogenic process via cytokines such as transforming growth factor-β and tumor necrosis factor. Preliminary results demonstrating amelioration of cytokine mediated lung-induced fibrosis in animal models with appropriate antibodies suggest a possible future modality of therapy. Certain amphiphilic drugs are capable of eliciting a more specific form of lung toxicity. This class of drugs can interfere with phospholipid metabolism in pulmonary macrophages. In these cases, phospholipidosis results from phospholipid accumulation. The physiologic sequelae in human phospholipidosis is still uncertain.

Macrophage epoxygenase determines a profibrotic transcriptome signature

Epoxygenases belong to the cytochrome P450 family. They generate epoxyeicosatrienoic acids, which are known to have anti-inflammatory effects, but little is known about their role in macrophage function. By high-throughput sequencing of RNA in primary macrophages derived from rodents and humans, we establish the relative expression of epoxygenases in these cells. Zinc-finger nuclease-mediated targeted gene deletion of the major rat macrophage epoxygenase Cyp2j4 (ortholog of human CYP2J2) resulted in reduced epoxyeicosatrienoic acid synthesis. Cyp2j4(-/-) macrophages have relatively increased peroxisome proliferator-activated receptor-γ levels and show a profibrotic transcriptome, displaying overexpression of a specific subset of genes (260 transcripts) primarily involved in extracellular matrix, with fibronectin being the most abundantly expressed transcript. Fibronectin expression is under the control of epoxygenase activity in human and rat primary macrophages. In keeping with the in vitro findings, Cyp2j4(-/-) rats show upregulation of type I collagen following unilateral ureter obstruction of the kidney, and quantitative proteomics analysis (liquid chromatography-tandem mass spectrometry) showed increased renal type I collagen and fibronectin protein abundance resulting from experimentally induced crescentic glomerulonephritis in these rats. Taken together, these results identify the rat epoxygenase Cyp2j4 as a determinant of a profibrotic macrophage transcriptome that could have implications in various inflammatory conditions, depending on macrophage function.

Safety and efficacy of ustekinumab or golimumab in patients with chronic sarcoidosis

Sarcoidosis is characterised by non-caseating granulomas that secrete pro-inflammatory cytokines, including interleukin (IL)-12, IL-23, and tumour necrosis factor (TNF)-α. Ustekinumab and golimumab are monoclonal antibodies that specifically inhibit IL-12/IL-23 and TNF-α, respectively. Patients with chronic pulmonary sarcoidosis (lung group) and/or skin sarcoidosis (skin group) received either 180 mg ustekinumab at week 0 followed by 90 mg every 8 weeks, 200 mg golimumab at week 0 followed by 100 mg every 4 weeks, or placebo. Patients underwent corticosteroid tapering between weeks 16 and 28. The primary end-point was week 16 change in percentage predicted forced vital capacity (ΔFVC % pred) in the lung group. Major secondary end-points were: week 28 for ΔFVC % pred, 6-min walking distance, St George's Respiratory Questionnaire (lung group), and Skin Physician Global Assessment response (skin group). At week 16, no significant differences were observed in ΔFVC % pred with ustekinumab (-0.15, p = 0.13) or golimumab (1.15, p = 0.54) compared with placebo (2.02). At week 28, there were no significant improvements in the major secondary end-points, although a nonsignificant numerically greater Skin Physician Global Assessment response was observed following golimumab treatment (53%) when compared with the placebo (30%). Serious adverse events were similar in all treatment groups. Although treatment was well tolerated, neither ustekinumab nor golimumab demonstrated efficacy in pulmonary sarcoidosis. However, trends towards improvement were observed with golimumab in some dermatological end-points.

Dysregulation of matricellular proteins is an early signature of pathology in laminin-deficient muscular dystrophy

Background

MDC1A is a congenital neuromuscular disorder with developmentally complex and progressive pathologies that results from a deficiency in the protein laminin α₂. MDC1A is associated with a multitude of pathologies, including increased apoptosis, inflammation and fibrosis. In order to assess and treat a complicated disease such as MDC1A, we must understand the natural history of the disease so that we can identify early disease drivers and pinpoint critical time periods for implementing potential therapies.

Results

We found that DyW mice show significantly impaired myogenesis and high levels of apoptosis as early as postnatal week 1. We also saw a surge of inflammatory response at the first week, marked by high levels of infiltrating macrophages, nuclear factor κB activation, osteopontin expression and overexpression of inflammatory cytokines. Fibrosis markers and related pathways were also observed to be elevated throughout early postnatal development in these mice, including periostin, collagen and fibronectin gene expression, as well as transforming growth factor β signaling. Interestingly, fibronectin was found to be the predominant fibrous protein of the extracellular matrix in early postnatal development. Lastly, we observed upregulation in various genes related to angiotensin signaling.

Methods

We sought out to examine the dysregulation of various pathways throughout early development (postnatal weeks 1-4) in the DyW mouse, the most commonly used mouse model of laminin-deficient muscular dystrophy. Muscle function tests (stand-ups and retractions) as well as gene (qRT-PCR) and protein levels (western blot, ELISA), histology (H&E, picrosirius red staining) and immunohistochemistry (fibronectin, TUNEL assay) were used to assess dysregulation of matricelluar protieins.

Conclusions

Our results implicate the involvement of multiple signaling pathways in driving the earliest stages of pathology in DyW mice. As opposed to classical dystrophies, such as Duchenne muscular dystrophy, the dysregulation of various matricellular proteins appears to be a distinct feature of the early progression of DyW pathology. On the basis of our results, we believe that therapies that may reduce apoptosis and stabilize the homeostasis of extracellular matrix proteins may have increased efficacy if started at a very early age.

Macrophage-like U937 cells recognize collagen fibrils with strain-induced discrete plasticity damage

At its essence, biomechanical injury to soft tissues or tissue products means damage to collagen fibrils. To restore function, damaged collagen must be identified, then repaired or replaced. It is unclear at present what the kernel features of fibrillar damage are, how phagocytic or synthetic cells identify that damage, and how they respond. We recently identified a nanostructural motif characteristic of overloaded collagen fibrils that we have termed discrete plasticity. In this study, we have demonstrated that U937 macrophage-like cells respond specifically to overload-damaged collagen fibrils. Tendons from steer tails were bisected, one half undergoing 15 cycles of subrupture mechanical overload and the other serving as an unloaded control. Both halves were decellularized, producing sterile collagen scaffolds that contained either undamaged collagen fibrils, or fibrils with discrete plasticity damage. Matched-pairs were cultured with U937 cells differentiated to a macrophage-like form directly on the substrate. Morphological responses of the U937 cells to the two substrates-and evidence of collagenolysis by the cells-were assessed using scanning electron microscopy. Enzyme release into medium was quantified for prototypic matrix metalloproteinase-1 (MMP-1) collagenase, and MMP-9 gelatinase. When adherent to damaged collagen fibrils, the cells clustered less, showed ruffled membranes, and frequently spread: increasing their contact area with the damaged substrate. There was clear structural evidence of pericellular enzymolysis of damaged collagen-but not of control collagen. Cells on damaged collagen also released significantly less MMP-9. These results show that U937 macrophage-like cells recognize strain-induced discrete plasticity damage in collagen fibrils: an ability that may be important to their removal or repair.

Oncostatin M modulates fibroblast function via signal transducers and activators of transcription proteins-3

Oncostatin M (OSM), an inflammatory cytokine of the interleukin-6 (IL-6) superfamily, plays a key role in various biological processes such as modulation of extracellular matrix (ECM), cell proliferation, cell survival, and induction of inflammation. It has been reported that OSM was increased in asthma and pulmonary fibrosis, and thus OSM may play a role in airway remodeling and the development of lung parenchymal fibrosis. Recruitment of lung fibroblasts to the sites of airway injury and subsequent differentiation into myofibroblasts is believed to contribute to excess ECM deposition. In the current study, we assessed the ability of OSM to modulate fibroblast collagen gel contraction, migration toward fibronectin, and expression of α-smooth muscle actin (α-SMA). We demonstrated that OSM augments gel contraction, chemotaxis, and α-SMA expression. OSM-augmented fibroblast chemotaxis was mediated by the signal transducer and activator of transcription (STAT3) and p38 mitogen-activated protein kinase, while augmentation on gel contraction and α-SMA expression was mediated by STAT3. Neither transforming growth factor-β1 nor PGE2 was involved in mediating OSM effect on the cells. The Th2 cytokines IL-4 and IL-13, which also are believed to play an important role in promoting lung fibrosis and airway remodeling, act through STAT3, and we demonstrated the potential for additive effects of OSM with IL-4 and IL-13. The present study supports the concept that OSM may contribute to tissue remodeling, which may be additive with IL-4 or IL-13. Blockade of OSM or OSM-mediated STAT3 signaling could be a therapeutic target to regulate lung fibrotic mechanisms.

Anti-scarring properties of different tryptophan derivatives

Hypertrophic scars are associated with prolonged extracellular matrix (ECM) production, aberrant ECM degradation and high tissue cellularity. Routinely used antifibrotic strategies aim to reduce ECM deposition and enhance matrix remodeling. Our previous study investigating the antifibrotic effects of indoleamine2, 3 dioxygenase (IDO) led to the identification of kynurenine (Kyn) as an antiscarring agent. A topical antifibrogenic therapy using Kyn is very attractive; however, it is well established that Kyn passes the blood brain barrier (BBB) which causes complications including excitatory neuronal death. Here we investigated the antiscarring properties of kynurenic acid (KynA), a downstream end product of Kyn that is unlikely to pass the BBB, as an effective and safe replacement for Kyn. Our results indicated that while not having any adverse effect on dermal cell viability, KynA significantly increases the expression of matrix metalloproteinases (MMP1 and MMP3) and suppresses the production of type-I collagen and fibronectin by fibroblasts. Topical application of cream containing KynA in fibrotic rabbit ear significantly decreased scar elevation index (1.13±0.13 vs. 1.61±0.12) and tissue cellularity (221.38±21.7 vs. 314.56±8.66 cells/hpf) in KynA treated wounds compared to controls. KynA treated wounds exhibited lower levels of collagen deposition which is accompanied with a significant decrease in type-I collagen and fibronectin expression, as well as an increase in MMP1 expression compared to untreated wounds or wounds treated with cream only. The results of this study provided evidence for the first time that KynA is promising candidate antifibrogenic agent to improve healing outcome in patients at risk of hypertrophic scarring.

Clinical experimentation with aerosol antibiotics: current and future methods of administration

Currently almost all antibiotics are administered by the intravenous route. Since several systems and situations require more efficient methods of administration, investigation and experimentation in drug design has produced local treatment modalities. Administration of antibiotics in aerosol form is one of the treatment methods of increasing interest. As the field of drug nanotechnology grows, new molecules have been produced and combined with aerosol production systems. In the current review, we discuss the efficiency of aerosol antibiotic studies along with aerosol production systems. The different parts of the aerosol antibiotic methodology are presented. Additionally, information regarding the drug molecules used is presented and future applications of this method are discussed.

Profibrotic activities for matrix metalloproteinase-8 during bleomycin-mediated lung injury

Matrix metalloproteinase-8 (MMP-8) is a potent interstitial collagenase thought to be expressed mainly by polymorphonuclear neutrophils. To determine whether MMP-8 regulates lung inflammatory or fibrotic responses to bleomycin, we delivered bleomycin by the intratracheal route to wild-type (WT) versus Mmp-8(-/-) mice and quantified MMP-8 expression, and inflammation and fibrosis in the lung samples. Mmp-8 steady state mRNA and protein levels increase in whole lung and bronchoalveolar lavage samples when WT mice are treated with bleomycin. Activated murine lung fibroblasts express Mmp-8 in vitro. MMP-8 expression is increased in leukocytes in the lungs of patients with idiopathic pulmonary fibrosis compared with control lung samples. Compared with bleomycin-treated WT mice, bleomycin-treated Mmp-8(-/-) mice have greater lung inflammation, but reduced lung fibrosis. Whereas bleomycin-treated Mmp-8(-/-) and WT mice have similar lung levels of several pro- and antifibrotic mediators (TGF-β, IL-13, JE, and IFN-γ), Mmp-8(-/-) mice have higher lung levels of IFN-γ-inducible protein-10 (IP-10) and MIP-1α. Genetically deleting either Ip-10 or Mip-1α in Mmp-8(-/-) mice abrogates their lung inflammatory response to bleomycin, but reconstitutes their lung fibrotic response to bleomycin. Studies of bleomycin-treated Mmp-8 bone marrow chimeric mice show that both leukocytes and lung parenchymal cells are sources of profibrotic MMP-8 during bleomycin-mediated lung fibrosis. Thus, during bleomycin-mediated lung injury, MMP-8 dampens the lung acute inflammatory response, but promotes lung fibrosis by reducing lung levels of IP-10 and MIP-1α. These data indicate therapeutic strategies to reduce lung levels of MMP-8 may limit fibroproliferative responses to injury in the human lung.

Ly6Chi monocytes direct alternatively activated profibrotic macrophage regulation of lung fibrosis

RATIONALE

Idiopathic pulmonary fibrosis (IPF) is a devastating disease. Antiinflammatory therapies, including corticosteroids, are of no benefit. The role of monocytes and macrophages is therefore controversial.

OBJECTIVES

To define the role of monocytes and macrophages during lung fibrogenesis and resolution, and explore the phenotype of the cells involved.

METHODS

We used multiple in vivo depletional strategies, backed up by adoptive transfer techniques. Further studies were performed on samples from patients with IPF.

MEASUREMENTS AND MAIN RESULTS

Depletion of lung macrophages during fibrogenesis reduced pulmonary fibrosis as measured by lung collagen (P = 0.0079); fibrosis score (P = 0.0051); and quantitative polymerase chain reaction for surrogate markers of fibrosis Col1 (P = 0.0083) and a-smooth muscle actin (P = 0.0349). There was an associated reduction in markers of the profibrotic alternative macrophage activation phenotype, Ym1 (P = 0.0179), and Arginase 1. The alternative macrophage marker CD163 was expressed on lung macrophages from patients with IPF. Depletion of Ly6Chi circulating monocytes reduced pulmonary fibrosis (P = 0.0052) and the number of Ym1- positive alternatively activated lung macrophages (P = 0.0310). Their adoptive transfer during fibrogenesis exacerbated fibrosis (P = 0.0304); however, adoptively transferred CD45.1 Ly6Chi cells were not found in the lungs of recipient CD45.2 mice.

CONCLUSIONS

We demonstrate the importance of circulating monocytes and lung macrophages during pulmonary fibrosis, and emphasize the importance of the alternatively activated macrophage phenotype. We show that Ly6Chi monocytes facilitate the progression of pulmonary fibrosis, but are not obviously engrafted into lungs thereafter. Finally, we provide empirical data to suggest that macrophages may have a resolution-promoting role during the reversible phase of bleomycin-induced pulmonary fibrosis.

IL-4 induces differentiation of human embryonic stem cells into fibrogenic fibroblast-like cells

BACKGROUND

Fibroblast heterogeneity is recognized, and fibroblasts from diseased tissues, including those of asthmatic subjects, have functional phenotypes that differ from normal tissue. However, progenitor-progeny relationships and the factors that control fibroblast differentiation are poorly defined.

OBJECTIVE

We sought to determine whether IL-4 could alter the functional phenotype of fibroblasts during their differentiation from stem/progenitor cells.

METHODS

Using a 3-dimensional collagen gel system, we obtained embryoid bodies derived from human embryonic stem cells and recovered spindle-shaped cells consistent with fibroblasts that had differentiated in the presence or absence of IL-4.

RESULTS

IL-4-induced fibroblast-like cells were more active in contraction of collagen gels, migration, and production of fibronectin than control (without IL-4) cells. IL-4-induced cells demonstrated less expression of miR-155, which modulated contraction, migration, and fibronectin production. These differences persisted in culture without further addition of IL-4, suggesting the differentiated phenotype might be a permanent alteration.

CONCLUSION

The current study demonstrates that IL-4 induces differentiation of stem/precursor cells into fibroblast-like cells that demonstrate a more fibrogenic phenotype, which is due to reduced expression of miR-155. These findings provide a novel mechanism for the persistent abnormalities in IL-4-related diseases and a novel target to regulate tissue remodeling by fibroblasts.

What can in vitro models of COPD tell us?

Chronic obstructive pulmonary disease (COPD) is a progressive lung disease characterised by chronic bronchitis, largely irreversible remodelling of the small airways, and emphysematous destruction of the alveoli. COPD is projected to be the third leading cause of death worldwide by 2020. COPD often results from prolonged exposure to irritants such as cigarette smoke or inhaled particulates. Current pharmacotherapies for COPD are unable to reverse the pathological changes of this disease, and this is partially due to a limited understanding of the intricate mechanisms by which chronic exposure lead to the different pathological components of COPD. This review examines how the mechanisms that underlie various components of COPD can be modelled in vitro, specifically using cigarette smoke extract with cells cultured from primary human lung tissue, and how the effectiveness of current and novel pharmacotherapies on successfully attenuating these pathological changes can also be examined in vitro.

Macrophage-derived biomarkers of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a severe, rapidly progressive diffuse lung disease. Several pathogenetic mechanisms have been hypothesized on the basis of the fibrotic lung damage occurring in this disease, and a potential profibrotic role of activated alveolar macrophages and their mediators in the pathogenesis of IPF was recently documented. This paper focuses on recent literature on potential biomarkers of IPF derived from activated alveolar macrophages. Biomarker discovery and clinical application are a recent topic of interest in the field of interstitial lung diseases (ILDs). Cytokines, CC-chemokines, and other macrophage-produced mediators are the most promising prognostic biomarkers. Many molecules have been proposed in the literature as potential biomarker of IPF; however, a rigorous validation is needed to confirm their clinical utility.

N-acetyl-L-cysteine inhibits TGF-beta1-induced profibrotic responses in fibroblasts

BACKGROUND

Excessive production of TGF-beta(1) plays a key role in the tissue remodeling or fibrotic process observed in bronchial asthma, chronic pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF). TGF-beta(1) has been reported to decrease the intracellular glutathione level and stimulate the production of reactive oxygen species.

OBJECTIVES

The aim of this study was to evaluate whether the antioxidant N-acetyl-l-cysteine (NAC) can affect TGF-beta(1)-mediated tissue remodeling in fibroblasts or modulate the production of fibronectin and vascular endothelial growth factor (VEGF) which are believed to be important mediators of tissue repair and remodeling.

METHODS

To accomplish this, human fetal lung fibroblasts (HFL-1) were used to assess the effect of NAC on the TGF-beta(1)-mediated contraction of floating gels and the TGF-beta(1)-induced mediator production. In addition, the effect of NAC on the TGF-beta(1)-induced differentiation to myofibroblasts was evaluated by assessing alpha-smooth muscle actin (alpha-SMA) expression.

RESULTS

NAC significantly abolished the TGF-beta(1)-augmented gel contraction (at 3mM, gel size 63.4+/-2.6% vs. 39.1+/-4.1%; p<0.01) compared with control in a concentration-dependent manner. NAC also significantly inhibited the TGF-beta(1)-augmented fibronectin (p<0.01) and VEGF (p<0.01) production in the media of both the three-dimensional gel and monolayer culture. Furthermore, NAC reversed the TGF-beta(1)-stimulated alpha-SMA expression (p<0.01).

CONCLUSION

These results suggest that NAC can affect the TGF-beta(1)-induced tissue remodeling or fibrotic process in vitro.

New perspectives in the treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is the most frequent idiopathic interstitial pneumonia with a prevalence ranging from 5 to 15 per 100,000 persons, and above 175 per 100,000 in the older population. IPF is a relentlessly progressive fibrotic lung disorder leading to death within a median duration of 3 years. It was hypothesized in the 1970s that pulmonary fibrosis initiates as an "alveolitis" progressing to interstitial fibrosis with connective tissue deposition, derangement of the lung architecture and functional impairment. However, in vitro studies indicated that alveolar/bronchiolar injured epithelial cells can drive the fibrotic process in the absence of macrophages and with minimal inflammation. This, together with the inability of classic immunosuppressive therapy to cure IPF, generated new pathogenesis paradigms and intense research into the role of the lack or the excessive production of anti-fibrotic or profibrotic mediators, oxidant injury, exaggerated coagulation, thus leading to investigate new treatment strategies. Preliminary results of some of such trials have shown significant reductions in lung function decline, disease exacerbation and mortality.

Fibronectin in formation and degradation of the pericellular matrix

Fibronectin is a large multifunctional glycoprotein present both in soluble form in plasma and other body fluids and in an insoluble form in interstitial connective tissues and in association with most basement membranes. The protein seems to provide a link between circulating body fluids, cell surfaces and the extracellular matrix. At sites of injury, fibronectin, covalently cross-linked to the fibrin clot, may provide a growth substratum for the invading cells and appears through its multiple interactions with other matrix components and cell surfaces to be involved in the organization of the matrix that will replace the clot. Fibronectin deposition may serve as a useful early marker for connective tissue formation in pathological processes and its fragmentation may serve as an indicator of pathological conditions involving proteolytic events.

Biochemical pathways leading to collagen deposition in pulmonary fibrosis

Fibrosis in the lung is well described histologically. There is destruction of the normal architecture with the appearance of inflammatory cells and connective tissue components, particularly collagen. Biochemical evidence for an increased deposition of collagen in man has been demonstrated in patients with both acute and chronic forms of pulmonary fibrosis. Studies of collagen metabolism in man are equivocal but there is convincing evidence for an increased synthesis rate in animal models of pulmonary fibrosis. Collagen degradation has been little studied but may be important, given the recent evidence indicating quite rapid turnover of lung collagen and a decreased degradation of collagen in experimental disease. The distribution of collagen types has been studied in man, where there is some evidence for the production of type III collagen in the early active phase of disease with a preponderance of type I collagen in the late stages. The cellular mechanisms leading to these changes are uncertain but the alveolar macrophage may play a central role, since it is capable of releasing factors which expand the fibroblast population as well as attracting new fibroblasts to the site of injury. These pathways are described for what is essentially the normal physiological response of scar formation, which has pathological consequences in the lung, a tissue requiring thin membranes at its epithelial and endothelial surfaces, in order to perform its main function of gas exchange.

Sphingosine 1-phosphate potentiates human lung fibroblast chemotaxis through the S1P2 receptor

Migration of fibroblasts plays an essential role in tissue repair after injury. Sphingosine 1-phosphate (S1P) is a multifunctional mediator released by many cells that can be released in inflammation and after injury. This study evaluated the effect of S1P on fibroblast chemotaxis toward fibronectin. S1P alone did not affect fibroblast migration, but S1P enhanced fibronectin-directed chemotaxis in a concentration-dependent manner. The effect of S1P was not mimicked by dihydro (dh) S1P or the S1P(1) receptor agonist SEW2871. S1P augmentation of fibroblast chemotaxis, however, was completely blocked by JTE-013, an S1P(2) antagonist, but not by suramin, an S1P(3) antagonist. Suppression of the S1P(2) receptor by small interfering (si)RNA also completely blocked S1P augmentation of fibroblast chemotaxis to fibronectin. S1P stimulated Rho activation and focal adhesion kinase (FAK) phosphorylation, and these were also significantly inhibited by the S1P(2) receptor antagonist (JTE-013) or by S1P(2) siRNA. Further, the potentiation of S1P signaling was blocked by the Rho-kinase inhibitor Y-27632 in a concentration-dependent manner. Inhibition of FAK with siRNA reduced basal chemotaxis toward fibronectin slightly but significantly, and almost completely blocked S1P augmented chemotaxis. These results suggest that S1P-augmented fibroblast chemotaxis toward fibronectin depends on the S1P(2) receptor and requires Rho and Rho-kinase, and FAK phosphorylation. By augmenting fibroblast recruitment, S1P has the potential to modulate tissue repair after injury. The pathways by which S1P mediates this effect, therefore, represent a potential therapeutic target to affect tissue repair and remodeling.

Cultured lung fibroblasts from ovalbumin-challenged "asthmatic" mice differ functionally from normal

Asthmatic airway remodeling is characterized by goblet cell hyperplasia, angiogenesis, smooth muscle hypertrophy, and subepithelial fibrosis. This study evaluated whether acquired changes in fibroblast phenotype could contribute to this remodeling. Airway and parenchymal fibroblasts from control or chronically ovalbumin (OVA)-sensitized and challenged "asthmatic" mice were assessed for several functions related to repair and remodeling +/- exogenous transforming growth factor (TGF)-beta. All OVA-challenged mouse fibroblasts demonstrated augmented gel contraction (P < 0.05) and chemotaxis (P < 0.05); increased TGF-beta(1) (P < 0.05), fibronectin (P < 0.05), and vascular endothelial growth factor (P < 0.05) release; and expressed more alpha-smooth muscle actin (P < 0.05). TGF-beta(1) stimulated both control and asthmatic fibroblasts, which retained all differences from control fibroblasts for all features(P < 0.05, all comparisons). Parenchymal fibroblasts proliferated more rapidly (P < 0.05), while airway fibroblasts proliferated similarly compared with control fibroblasts (P = 0.25). Thus, in this animal model, OVA-challenged mouse fibroblasts acquire a distinct phenotype that differs from control fibroblasts. The augmented profibrotic activity and mediator release of asthmatic fibroblasts could contribute to airway remodeling in asthma.

Pharmacokinetic and Pharmacodynamic Efficacy of Intrapulmonary Administration of Ciprofloxacin for the Treatment of Respiratory Infections

The pharmacokinetic and pharmacodynamic efficacy of intrapulmonary administration of ciprofloxacin (CPFX) for the treatment of respiratory infections caused by pathogenic microorganisms resisting sterilization systems of alveolar macrophages (AMs) was evaluated by comparison with an oral administration. The time-courses of the concentration of CPFX in AMs and lung epithelial lining fluid (ELF) following intrapulmonary administration of CPFX solution to rats (200 microg/kg) were markedly higher than that following oral administration (10 mg/kg). The time-course of the concentrations of CPFX in plasma following intrapulmonary administration was markedly lower than that in AMs and ELF. These results indicate that intrapulmonary administration is more effective in delivering CPFX to AMs and ELF, compared with oral administration, in spite of a low dose and it avoids distribution of CPFX to the blood. In addition, the antibacterial effects of CPFX in AMs and ELF following intrapulmonary administration were evaluated by pharmacokinetics/pharmacodynamics analysis. The concentration of CPFX in AMs and ELF-time curve (AUC)/minimum inhibitory concentration of CPFX (MIC) ratio and the maximum concentration of CPFX in AMs and ELF (Cmax)/MIC ratio were markedly higher than the effective values. The present study indicates that intrapulmonary administration of CPFX is an effective technique for the treatment of respiratory infections.

Reactive Nitrogen Species Augment Fibroblast-Mediated Collagen Gel Contraction, Mediator Production, and Chemotaxis

Reactive nitrogen species (RNS) such as peroxynitrite cause cellular injury and tissue inflammation. Excessive production of nitrotyrosine, which is a footprint of RNS, has been observed in the airways of patients with asthma and chronic obstructive pulmonary disease, disorders characterized by tissue remodeling. The aim of this study was to evaluate whether RNS can affect tissue remodeling through direct effects on fibroblasts, and to determine if these effects depend on production of transforming growth factor-beta (TGF-beta). To accomplish this, human fetal lung fibroblasts (HFL-1) were used to assess fibroblast-mediated contraction of floating gels and chemotaxis toward fibronectin. In addition, the ability of fibroblasts to release TGF-beta1, fibronectin, and vascular endothelial growth factor (VEGF) was assessed by enzyme-linked immunosorbent assay. Authentic peroxynitrite significantly augmented gel contraction (P < 0.01) and chemotaxis (P < 0.01) compared with control in a concentration-dependent manner. Similarly, the peroxynitrite donor 3-morpholynosidenonimine hydrochloride (SIN-1) also augmented gel contraction (P < 0.01). RNS also significantly increased TGF-beta1 (P < 0.01), fibronectin (P < 0.01), and VEGF (P < 0.01) release into the media in both 3D gel and monolayer culture. Anti-TGF-beta antibody reversed RNS-augmented gel contraction (P < 0.01) and mediator production (P < 0.01). Anti-TGF-beta antibody also partially, but significantly, reversed RNS-augmented chemotaxis toward fibronectin (P < 0.01). Finally, peroxynitrite enhanced expression of alpha5beta1 integrin, which is a receptor for fibronectin (P < 0.01), and neutralizing anti-TGF-beta antibody suppressed peroxynitrite-augmented alpha5beta1 expression (P < 0.01). These results suggest that RNS can affect the tissue repair process by modulating TGF-beta1.

Discoidin domain receptor 1 contributes to the survival of lung fibroblast in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF), characterized by fibroblast proliferation and accumulation of extracellular matrix, including collagen, is a chronic progressive disorder that results in lung remodeling and fibrosis. However, the cellular mechanisms that may make fibroblasts resistant to apoptosis have not been completely elucidated. Discoidin domain receptor 1 (DDR1), a receptor tyrosine kinase whose ligand is collagen, is expressed in vivo and contributes in vitro to leukocyte differentiation and nuclear factor (NF)-kappaB activation, which may play an important role in fibroblast survival. In this study, we examined in vivo and in vitro DDR1 expression and its role in cell survival using fibroblasts obtained from IPF and non-IPF patients. Immunohistochemically, fibroblasts present in fibroblastic foci expressed endogenous DDR1. The DDR1 expression level was significantly higher in fibroblasts from IPF patients, and the predominant isoform was DDR1b. In IPF patients, DDR1 activation in fibroblasts inhibited Fas ligand-induced apoptosis and resulted in NF-kappaB nuclear translocation. Suppression of DDR1 expression in fibroblasts by siRNA abolished these effects, and an NF-kappaB inhibitor abrogated the anti-apoptotic effect of DDR1 activation. We propose that DDR1 contributes to fibroblast survival in the tissue microenvironment of IPF and that DDR1 up-regulation may occur in other fibroproliferative lung diseases as well.

A vicious circle of alveolar macrophages and fibroblasts perpetuates pulmonary fibrosis via CCL18

RATIONALE

Recently, models of macrophage activation have been revised. Macrophages stimulated with Th2 cytokines have been classified as alternatively activated.

OBJECTIVES

This article examines the expression and regulation of CC chemokine ligand 18 (CCL18), a marker of alternative activation, by human alveolar macrophages (AMs).

METHODS

AM were obtained from bronchoalveolar lavage (BAL) fluid of patients with idiopathic pulmonary fibrosis, sarcoidosis, or hypersensitivity pneumonitis (n = 69) and healthy volunteers (n = 22). Expression of CCL18 was determined by quantitative reverse transcriptase-polymerase chain reaction, in situ hybridization, flow cytometry, and immunohistochemistry, respectively.

MEASUREMENTS AND MAIN RESULTS

Spontaneous CCL18 production by BAL-derived cells was markedly increased in patients with pulmonary fibrosis and correlated negatively with pulmonary function test parameters. CCL18 gene expression and protein production were up-regulated in normal AMs after Th2 cytokine stimulation and/or coculture with human lung fibroblasts. Native collagen significantly up-regulated CCL18 expression in normal AMs activated with Th2 cytokines via a mechanism mediated by beta2-integrin/ scavenger receptor(s). Culture supernatants of AMs from patients with idiopathic pulmonary fibrosis increased collagen production by normal lung fibroblasts partly mediated via CCL18.

CONCLUSIONS

Our findings suggest that AMs from patients with pulmonary fibrosis disclose a phenotype of alternative activation and might be a part of a positive feedback loop with lung fibroblasts perpetuating fibrotic processes.

One in vitro model for visceral adipose-derived fibroblasts in chronic inflammation

One pathogenesis of the obesity-associated complications is that consistent with increased body fat mass, the elevation of adipose tissue-derived cytokines inflicts a low-grade chronic inflammation, which ultimately leads to metabolic disorders. Adipocytes and macrophages in visceral adipose (VA) have been confirmed to contribute to the chronic inflammation; however, the role of the resident fibroblasts is still unknown. We established one VA fibroblast cell line, termed VAFC. Morphological analysis indicated that there were large numbers of pits at the cell plasma membrane. In vitro VAFC cells promoted bone marrow cells to differentiate into macrophages and protected them from apoptosis in the serum-free conditions. Additionally, they also interfered in lymphocytes proliferation. On the basis of these results, this cell line might be an in vitro model for understanding the role of adipose-derived fibroblasts in obesity-associated chronic inflammation.

Leukotriene D4 potentiates fibronectin-induced migration of human lung fibroblasts

Fibroblasts play an important role in the repair and remodeling processes following injury. Leukotriene D4 (LTD4) is a potent mediator in inflammatory processes, but the direct effect of cysteinyl leukotrienes on fibroblast migration remains unelucidated. In this study, the effect of the LTD4 on normal human lung fibroblasts (NHLF) chemotaxis induced by human plasma fibronectin (HFn) was investigated using the modified Boyden's chamber technique. LTD4 potentiated NHLF chemotaxis to HFn in concentration-dependent manner. A specific cysteinyl leukotriene receptor type 1 antagonist, pranlukast inhibited this effect, indicating that LTD4 affected cell migration via its specific receptor. The potentiating effect of LTD4 on fibroblast chemotaxis was completely abolished by pertussis toxin (PTX), suggesting that LTD4-induced effect was dependent on PTX-sensitive Gi/o signaling. These findings suggest that LTD4 has a potential to augment fibroblast chemotaxis, and to contribute to regulation of the wound healing and following remodeling in fibrotic processes of the lung.

Varied low density lipoprotein binding property of proteoglycans synthesized by vascular smooth muscle cells cultured on extracellular matrix

Earlier we showed that the extracellular matrix (ECM) secreted by vascular cells modulated proteoglycan synthesis by vascular smooth muscle cells in culture and altered the proteoglycan characteristics. In this study, we tested the hypothesis that these ECM-mediated alterations increased the affinity of the proteoglycans for plasma low density lipoprotein (LDL). Newly synthesized proteoglycans were isolated from smooth muscle cells cultured on the ECMs secreted by vascular endothelial cells, smooth muscle cells, or THP-1 macrophages and their binding affinity for LDL determined. Proteoglycans from all cultures contained sub-fractions that bound LDL with low and high affinity. However, compared with the cells plated on the endothelial cell ECM, the cells plated on the smooth muscle cell ECM and macrophage ECM synthesized significantly more high affinity proteoglycans. Removal of collagen, elastin, and chondroitin sulfates from the smooth muscle cell ECM and chondroitin sulfates from the macrophage ECM increased the production of high affinity proteoglycans by 15-22%. However, neutralization of fibronectin from both ECMs decreased the high affinity proteoglycans by 20%. Removal of matrix-bound growth factors had no effect on the synthesis of high affinity proteoglycans. Compared with the low affinity proteoglycans, the high affinity proteoglycans were larger, more sulfated and contained higher proportions of chondritin sulfate, dermatan sulfate, and N-sulfated heparan sulfate chains. These results suggest that the ECM-mediated alterations in vascular smooth muscle cell proteoglycans may lead to increased deposition of LDL in the arterial wall.

Integrin alpha4beta1 regulates migration across basement membranes by lung fibroblasts: a role for phosphatase and tensin homologue deleted on chromosome 10

Idiopathic pulmonary fibrosis is a disease that is characterized by fibroblast accumulation and activation in the distal airspaces of the lung. We hypothesized that fibrotic lung fibroblasts migrate/invade across basement membranes by integrin-mediated mechanisms as a means of entering alveoli. We demonstrate that in lung fibroblasts derived from patients with idiopathic pulmonary fibrosis, fibronectin signaling is both necessary and sufficient for basement membrane migration/invasion across basement membranes. This effect is mediated through the alpha5beta1 integrin because blockade of fibronectin-alpha5 integrin ligation attenuated this response. In contrast, ligation of alpha4beta1 integrin inhibits basement membrane invasion by normal lung fibroblasts but not by fibrotic lung fibroblasts. This phenotypic difference is not related to surface expression of the alpha4beta1 integrin, as demonstrated by flow cytometry. In normal lung fibroblasts but not in fibrotic lung fibroblasts, we show that ligation of alpha4beta1 integrin induces a significant increase in phosphatase and tensin homologue deleted on chromosome 10 (PTEN) activity. Fibrotic lung fibroblasts express constitutively less PTEN mRNA and protein as well as phosphatase activity in comparison to normal lung fibroblasts. Together, these data suggest that a loss of alpha4beta1 signaling via PTEN confers a migratory/invasive phenotype to fibrotic lung fibroblasts. Furthermore, this study implicates a loss of PTEN function in the pathophysiology of idiopathic pulmonary fibrosis.

Systemic sclerosis: the susceptible host (genetics and environment)

It is becoming evident that several genetic factors participate in modulating susceptibility to SSc and its clinical manifestations. Some genes that specifically affect ECM metabolism and vascular function may be unique to SSc and scleroderma-related disorders; others, such as those genes involved in regulating immune tolerance, are likely shared with other autoimmune diseases. The effect of genetic variations (or polymorphisms) that are found in most of these genes taken individually will likely have only a small or modest effect on disease risk; only a few genetic variations are expected to be highly penetrant. Moreover, genetic studies in SSc have to deal with the additional issues of heterogeneous phenotypes, low disease prevalence in the general population, and an even greater paucity of multiplex families that makes traditional linkage studies difficult, if not impossible. Alternative approaches include allelic association studies, but conventional case-controls designs may be subject to selection bias and will require large sample sizes if the genes that are under investigation confer only modest (OR = 1.5-2.0) disease risk (Fig. 2). The simultaneous examination of several genes that are biologically relevant to a specific disease process to attain higher aggregate ORs, is one approach that was used in several reports that were cited in this review. The use of family-based controls, such as in the transmission-disequilibrium test (based on assessment of the transmitted or nontransmitted alleles that are associated with disease from heterozygous parents to affected offspring), would provide more robustness to spurious associations from population stratification, but is actually less powerful and efficient than case-control designs. Furthermore, for many late adult-onset diseases the effort required to obtain samples from living parents are for a variety of reasons not trivial. The success of these allelic association-based approaches depends on the identification of likely candidate disease genes (or at least markers in disequilibrium with disease genes), careful definition/ascertainment of disease phenotypes to minimize genetic heterogeneity, and for case-control designs, strategies to account for population stratification or admixture. The identification of candidate genes will be aided by rapid progress in the Human Genome Project and other genome efforts that will eventually identify all human genetic variations. Although this will lead to better understanding of the genes that might be involved in complex diseases, much work is required to understand the basic biology of how disease genotypes become clinical phenotypes. This is especially daunting in complex diseases, such as SSc, where the phenotype (including disease susceptibility and clinical presentation) is influenced by dynamic interactions between genetic variations and environment. Multi-center collaborative efforts with research paradigms that integrate genetic and environmental factors (including sociodemographic variables) will be required to elucidate the contribution of environment and genetics in the pathogenesis of SSc.