Pathogenesis of the granulomatous lung diseases

Update on Treatment in Cardiac Sarcoidosis

OPINION STATEMENT

The prevalence of cardiac sarcoidosis has exponentially increased over the past decade, primarily due to increased awareness and diagnostic modalities for the disease entity. Despite an expanding patient cohort, the optimal management of cardiac sarcoidosis remains yet to be established with a significant lack of prospective trials to support current practice. Corticosteroids remain first-line treatment of this disorder, and we recommend that immunosuppressive therapy should be initiated in all patients diagnosed with cardiac sarcoidosis. Additional pharmacotherapy may be necessary based on disease manifestations and response to treatment. The use of nuclear imaging with ¹⁸fluorodeoxyglucose (¹⁸FDG) positron emission tomography (PET) to guide treatment has become more common, but lacks rigorous data from larger cohorts. Whether an improvement in inflammatory burden as assessed by ¹⁸FDG-PET is correlated with clinical outcomes is as yet unproven. Device therapy with implantable-cardioverter defibrillators should be considered in all cardiac sarcoidosis patients for either primary or secondary prevention of ventricular arrhythmias and cardiac death.

Stachybotrys chartarum-induced hypersensitivity pneumonitis is TLR9 dependent

Hypersensitivity pneumonitis (HP), an inflammatory lung disease, develops after repeated exposure to inhaled particulate antigen and is characterized by a vigorous T helper type 1-mediated immune response, resulting in the release of IL-12 and interferon (IFN)-γ. These T helper type 1 cytokines may participate in the pathogenesis of HP. Stachybotrys chartarum (SC) is a dimorphic fungus implicated in a number of respiratory illnesses, including HP. Here, we have developed a murine model of SC-induced HP that reproduces pathology observed in human HP and hypothesized that toll receptor-like 9 (TLR9)-mediated dendritic cell responses are required for the generation of granulomatous inflammation induced by inhaled SC. Mice sensitized and challenged with 10(6) SC spores develop granulomatous inflammation with multinucleate giant cells, accompanied by increased accumulation of neutrophils and CD4(+) and CD8(+) T cells. SC sensitization and challenge resulted in robust pulmonary expression of tumor necrosis factor-α, IL-12, and IFN-γ. SC-mediated granulomatous inflammation required IFN-γ and was TLR9 dependent, because TLR9(-/-) mice displayed reduced peribronchial inflammation, decreased accumulation and/or activation of polymorphonuclear (PMN) and CD4(+) and CD8(+) T cells, and reduced lung expression of type 1 cytokines and chemokines. T-cell production of IFN-γ was IL-12 dependent. Our studies suggest that TLR9 is critical for dendritic cell-mediated development of a type 1 granulomatous inflammation in the lung in response to SC.

Procaterol inhibits lung fibroblast migration

Fibroblasts are important cells that are involved in modulation of fibrosis after injuries. In some uncontrollable inflammatory processes, excess fibroblasts migrate around the small airway. The pathogenesis of chronic obstructive pulmonary disease is related to fibrosis around the small airways. The aim of the current study was to investigate the effect of procaterol, a second-generation beta (2)-agonist, on migration of human fetal lung fibroblasts (HFL-1) induced by human plasma fibronectin (HFn). Using the blindwell chamber technique, 10(-8) M procaterol inhibited migration of HFL-1 (control, 100%; 10(-8) M, 73.2 +/- 4.9%; n = 6, p < 0.05). The inhibitory effect of procaterol was concentration-dependent. Although a beta 2-receptor inhibitor, ICI 181551, blocked the inhibitory effect of procaterol, a beta 1-receptor inhibitor, atenolol, did not. Because a cyclic AMP-dependent protein kinase (PKA) inhibitor, KT5720, blocked the effect of procaterol, the cyclic AMP-PKA pathway may be involved in the migration inhibitory process. Procaterol, which is prescribed mainly for treatment of bronchial asthma, might be a useful drug for inhibiting lung fibrosis following injuries to the lung.

Gammadelta T cells and Th17 cytokines in hypersensitivity pneumonitis and lung fibrosis

Hypersensitivity pneumonitis (HP) is an inflammatory lung disease caused by the repeated inhalation of aerosolized antigens. With chronic exposure to an inhaled antigen, patients are at risk of developing irreversible pulmonary fibrosis as well as an increased morbidity and mortality. Although alphabeta T cells have been shown to be important in the pathogenesis of HP, gammadelta T cells also accumulate in the bronchoalveolar lavage of patients with HP. gammadelta T cells represent a distinct lymphocyte subset, whose primary function is not well understood. In contrast to alphabeta T cells, gammadelta T cells recognize unprocessed antigens, such as those upregulated on injured or stressed epithelial cells. In a murine model of HP induced by exposure to the ubiquitous microorganism Bacillus subtilis, gammadelta T cells expressing the canonical Vgamma6/Vdelta1 T cell receptor were dramatically expanded in the lung. The predominant cytokines expressed by this gammadelta T-cell subset were T-helper 17 (Th17) cytokines that were critical for bacterial clearance and the resolution of lung inflammation. Th17-expressing gammadelta T cells are also expanded in other murine models of lung infection and inflammation, which suggests that these cells play a sentinel role in mucosal immunity. Thus, an increased understanding of gammadelta T cells that express Th17 cytokines in HP and other inflammatory lung diseases may lead to the development of novel therapeutic and clinical strategies that prevent the development of fibrotic lung disease.

Regional fibroblast heterogeneity in the lung: implications for remodeling

RATIONALE

Excessive deposition of extracellular matrix occurs in proximal airways of individuals with asthma, but fibrosis in distal lung has not been observed. Whether differing fibrotic capacities of fibroblasts from these two regions contribute to this variability is unknown.

OBJECTIVES

We compared morphologic and functional characteristics of fibroblasts isolated from proximal airways and distal lung parenchyma to determine phenotypic differences.

METHODS

Concurrent proximal airway and distal lung biopsies were obtained by bronchoscopy from subjects with asthma to isolate airway and distal lung fibroblasts, respectively. The following characteristics were compared: morphology, proliferation, alpha-smooth muscle actin expression, and synthesis of procollagen type I and eotaxin-1.

RESULTS

Airway fibroblasts (AFs) are morphologically distinct from distal lung fibroblasts (DLFs): they are larger (2.3-fold greater surface area vs. matched DLFs; p = 0.02), stellate in appearance, and with more cytoplasmic projections compared with the spindle-shaped DLFs. AFs synthesized more procollagen type I than did DLFs at baseline (twofold higher; p = 0.003) and after transforming growth factor-beta stimulation (1.4-fold higher; p = 0.02). Similarly, AFs produced more eotaxin-1 than did DLFs at baseline (2.5-fold higher; p = 0.004) and after interleukin-13 stimulation (13-fold higher; p = 0.0001). In contrast, DLFs proliferate more than AFs with serum stimulation (about sixfold greater; p = 0.03). Unstimulated DLFs also expressed more alpha-smooth muscle actin than did corresponding AFs (p = 0.006).

CONCLUSIONS

These studies suggest that at least two phenotypes of fibroblast exist in the lung. These phenotypic differences may partially explain the variable responses to injury and repair between proximal airways and distal lung/parenchyma in asthma and other respiratory diseases.

Obstructive sarcoidosis

Sarcoidosis is a systemic granulomatous disease that frequently involves the lung. Although classically thought of as a restrictive lung disease, airway obstruction has become a recognized feature of the disease in the past years. Sarcoidosis can affect the airway at any level and when the involvement includes small airways, it can resemble more common obstructive airway diseases, such as asthma and chronic bronchitis. Pulmonary function testing and high-resolution computerized tomography of the chest are two important tools to evaluate the presence and extent of airway obstruction in sarcoidosis. Pharmacologic options for the treatment of obstructive sarcoidosis are, in large part, not supported by large, randomized clinical trials. In severe cases of bronchostenosis owing to sarcoidosis granuloma or extrinsic compression from intrathoracic lymphadenopathy, interventional bronchoscopy has successfully been performed, although repeated procedures are usually required. Lung transplantation is an ultimate option in selected patients with late-stage fibrotic disease.

Bradykinin stimulates type II alveolar cells to release neutrophil and monocyte chemotactic activity and inflammatory cytokines

In the present study, we evaluated the potential of bradykinin (BK) to induce the release of neutrophil and monocyte chemotactic activity (NCA and MCA) and cytokines from an alveolar type II epithelial cell line, A549 cells. BK stimulated A549 cells to release NCA and MCA in a dose- and time-dependent manner (P < 0.001). Checkerboard analysis revealed that both NCA and MCA involved chemotactic and chemokinetic activity. Molecular sieve column chromatography showed three molecular weight masses (near 19 kd, 8 kd, and 400 d) for NCA and several molecular weight peaks (near 66 kd, 25 kd, 19 kd, 16 kd, and 400 d) for MCA. The release of NCA and MCA was inhibited by cycloheximide and lipoxygenase inhibitors (P < 0.01). The NCA and MCA were inhibited by leukotriene B4 (LTB4) receptor antagonist (P < 0.01), and the concentration of LTB4 was high enough for NCA and MCA. Antibodies to interleukin (IL)-8 and granulocyte colony-stimulating factor (G-CSF) attenuated NCA (P < 0.01), and antibodies to monocyte chemotactic protein-1 (MCP-1), G-CSF, and transforming growth factor (TGF)-beta attenuated MCA (P < 0.01). The levels of IL-8, G-CSF, MCP-1, and TGF-beta increased time dependently (P < 0.01). BK also stimulated the release of ILeukin-6 from A549 cells (P < 0.001). The receptors responsible for the release of NCA, MCA, and individual chemokines involved both BKB1 and BKB2 receptors. These data suggest that BK may stimulate alveolar type II pneumocytes to release inflammatory cytokines, which then may modulate the lung inflammation.

Enhanced interleukin-8 release and gene expression in macrophages after exposure to Mycobacterium tuberculosis and its components

Mycobacterium tuberculosis infection is accompanied by acute and chronic inflammatory infiltrates associated with necrotizing granulomas in lung tissue. The cellular infiltrate is characterized by inflammatory cells which include neutrophils, lymphocytes, and macrophages. In animal and in vitro models of mycobacterial infection, cytokines including tumor necrosis factor-alpha (TNF-alpha), interferon gamma (IFN-gamma), and interleukin-1 beta (IL-1 beta) participate in granulomatous inflammation. We hypothesized that interleukin-3, a potent chemoattractant for neutrophils and lymphocytes, could be released by activated alveolar macrophages after exposure to M. tuberculosis or its components and contribute to granulomatous lung inflammation. A quantitative immunoassay revealed that IL-8 protein release was significantly elevated in supernatants of macrophages and in lavage fluid obtained from patients with pulmonary tuberculosis compared to normal controls. In addition, Northern blots demonstrated striking up-regulation of IL-8 mRNA in macrophages from these patients. M. tuberculosis and its cell wall components lipoarabinomannan (LAM), lipomannan (LM), and phosphoinositolmannoside (PIM) stimulated IL-8 protein release and mRNA expression in vitro from alveolar macrophages, but deacylated LAM did not. Neutralizing antibodies to TNF-alpha and/or IL-1-alpha and beta blocked 83% of the stimulation. IL-8 synthesis and release is an early response of macrophages after phagocytosis of M. tuberculosis. Its production serves to attract both acute and chronic inflammatory cells of active infection and thus participates in the process of containment of the pathogen.

Structure and neutrophil-activating properties of a novel inflammatory peptide (ENA-78) with homology to interleukin 8

A new neutrophil-activating peptide, termed ENA-78, was identified in the conditioned media of stimulated human type II epithelial cell line A549. In response to stimulation with either interleukin 1 beta (IL-1 beta) or tumor necrosis factor alpha (TNF-alpha), ENA-78 was produced and secreted concomitantly with IL-8, GRO alpha, and GRO gamma. ENA-78 consists of 78 amino acids [sequence; see text] and has a molecular weight of 8,357. It has four cysteines positioned identically to those of IL-8 and analogues, and thus belongs to the CXC family of peptides. ENA-78 is related to neutrophil-activating peptide 2 (NAP-2) and GRO alpha (sequence identity, 53% and 52%, respectively) and IL-8 (22% identity). Like NAP-2 and GRO alpha, ENA-78 stimulates neutrophils, inducing chemotaxis, a rise in intracellular free calcium and exocytosis. Cross-desensitization experiments indicate that ENA-78 acts through the same type of receptors as IL-8, NAP-2, and GRO alpha.

Alveolar macrophages from patients with bronchogenic carcinoma and sarcoidosis similarly express monocyte antigens

It has been shown that bronchoalveolar lavages (BALs) from patients with sarcoidosis and other interstitial lung diseases contain abnormally increased numbers of alveolar macrophages (AM) expressing antigens found on monocytes. The aim of this study was to compare the phenotype of AM from patients with sarcoidosis with those from patients with non-interstitial lung disease, namely carcinoma. Using a panel of monoclonal antibodies against cells of the mononuclear phagocytic series and immunohistochemical staining, we have compared the expression of antigens on AM recovered at BAL and peripheral blood monocytes from patients with sarcoidosis, with similar cell preparations from bronchogenic carcinoma patients and normal volunteers. We have shown that CD14, CR1 (CD35) and CR3 (CD11b, CD18) are expressed on the majority of monocytes from all subjects, but on only a minority of normal AM. In both patients with sarcoidosis and patients with bronchogenic carcinoma increased proportions of AM expressed these monocyte-associated antigens. Since BALs from the carcinoma patients were derived from lung lobes which were radiologically free of tumour, the accumulation of AM expressing monocytic antigens is not a local response to the tumour. We conclude that infiltration of the lung with monocytes is a more general response to lung disease than has hitherto been reported.

Interleukin-8 gene expression by a pulmonary epithelial cell line. A model for cytokine networks in the lung

Cellular constituents of the alveolar-capillary wall may be key participants in the recruitment of polymorphonuclear leukocytes to the lung through the generation of the novel neutrophil chemotactic peptide interleukin-8 (IL-8). This interaction appears to occur via the ability of human alveolar macrophage (AM)-derived monokines, tumor necrosis factor (TNF), and interleukin-1 (IL-1) to induce gene expression of IL-8 from pulmonary type II-like epithelial cells (A549). Northern blot analysis demonstrated that steady-state IL-8 mRNA expression, by either TNF- or IL-1 beta-treated A549 cells, occurred in both a dose- and time-dependent fashion. Similarly, extracellular antigenic IL-8, as assessed by specific ELISA, was expressed from TNF- or IL-1 beta-stimulated epithelial cells in a time-dependent fashion with maximal IL-8 antigen detected at 24 h poststimulation. Immunohistochemical staining utilizing rabbit anti-human IL-8 antibody identified immunoreactive, cell-associated IL-8 antigen as early as 8 h post-TNF or IL-1 beta stimulation. A549-generated neutrophil chemotactic bioactivity paralleled IL-8 steady-state mRNA levels. Signal specificity was demonstrated in this system as IL-8 mRNA or protein expression by lipopolysaccharide (LPS)-treated A549 cells was not different from unstimulated cells. Although LPS did not serve as a direct stimulus for the production of IL-8 by type II-like epithelial cells, the condition media from LPS-challenged AM induced a significant expression of IL-8 mRNA by the A549 cells. 24-h conditioned media from LPS-treated cells was as potent as either IL-1 beta or TNF in generating steady-state IL-8 mRNA by A549 cells. Preincubation of LPS-treated AM-conditioned media with anti-human TNF or IL-1 beta neutralizing antibodies resulted in significant abrogation of IL-8 gene expression by A549 pulmonary epithelial cells. These findings demonstrate potential cell-to-cell communication circuits that may be important between AMs and pulmonary epithelial cells during the recruitment phase of acute lung inflammation.

Effects of inflammation and fibrosis on pulmonary function in diffuse lung fibrosis

To investigate the relation between lung function and inflammation and fibrosis in patients with diffuse lung fibrosis, a study was made of untreated patients without appreciable airway obstruction (14 patients with cryptogenic fibrosing alveolitis and seven with pneumoconiosis). Quantitative assessment of inflammatory infiltration and fibrosis was carried out on open lung biopsy specimens and compared with lung volumes, carbon monoxide transfer factor (TLCO), TLCO corrected for alveolar volume (TLCO/VA), and arterial blood gases at rest and during exercise. The degree of fibrosis and the degree of cellular infiltration were positively correlated. Lung volumes and TLCO were correlated with the grades of fibrosis and cellular infiltration of alveoli; arterial blood gases during exercise tended to correlate with both fibrosis and infiltration (p less than 0.06). In contrast, morphological data were not correlated with gas exchange at rest or with TLCO/VA. It is concluded that, in untreated patients with diffuse lung fibrosis, lung volumes, TLCO, and arterial blood gases during exercise reflect the lung lesions, and that the pulmonary function tests used cannot discriminate between fibrosis and infiltration of the lung by inflammatory cells.

Bronchoalveolar lavage

The technique of BAL performed through the fiberoptic bronchoscope has, in two decades, provided clinicians and researchers with the ability to safely sample the inflammatory-immune cell milieu of the human lung. Standardized BAL and processing of the lavage constituents provides assistance in determining the optimal care of patients with a variety of lung diseases, and renders diagnosis in selected cases. It has become indispensable in the diagnosis of pulmonary infiltrates in immunocompromised patients, and plays an important role in improving clinical management. Finally, it continues to yield an ever increasing amount of data for the researchers studying the mechanisms and pathogenesis of lung disease. It is likely that BAL will become an even more valuable tool with increasing relevance to the practice of chest medicine in the 1990s.

Immune aspects of sarcoidosis

Although the initiating factor(s) is unknown, it is now accepted that pulmonary sarcoidosis develops as a result of an over-stimulated local cellular immune response. Starting as a lymphocytic alveolitis, there is a progression to granuloma formation within the interstitium as stimulated T lymphocytes release mediators capable of attracting and activating monocytes to differentiate into macrophages and epithelioid cells. We are also aware that macrophage-like cells must act as antigen presenters to initiate T cell stimulation within the immune response. To date, interest in the alveolar macrophages of patients with sarcoidosis has focused more on their passive role as responders of the soluble T cell products released as the disease progresses. This paper explores the active role of mononuclear non-lymphoid cells as inducers of immune responses, by taking advantage of monoclonal antibodies capable of discriminating between phenotypically distinct subsets of macrophages. Recent results are presented that suggest a central role for these cells in controlling the course of this disease, focusing specifically on the mechanisms underlying the failure in some patients to resolve the interstitial inflammation and subsequently progressing to fibrosis. A new hypothesis proposes that aberrations in the functional capacity of macrophages may prohibit the emergence of a granuloma-resolving mechanism in some sarcoid patients.

Establishment and characterization of an antigen-specific T-cell line from liver granulomas of Schistosoma mansoni-infected mice

Granulomatous inflammations in schistosomiasis mansoni are the result of T-cell-mediated reactions to soluble egg antigens (SEA) secreted by parasite ova. To study TDH effector cell function, a granuloma T-cell line was established from collagenase-digested liver granulomas of acutely infected CBA/J mice. Dispersed nonadherent granuloma cells were cultured with feeder layer cells and SEA or with feeder layer cells alone in alternate cycles for 32 weeks. The granuloma T-cell line was L3T4+ Lyt-1+. In vitro, the SEA-stimulated T cells showed proliferation and interleukin 2 production. One million T cells adoptively transferred SEA-specific footpad swelling, and 7.5 X 10(6) T cells adoptively transferred granulomatous hypersensitivity to injected ova or SEA-coated beads. Anti-L3T4 monoclonal antibody blocked the SEA-specific cell proliferation. Depletion of L3T4+ cells abrogated, while that of Lyt-1+ cells diminished the adoptive transfer of SEA-specific footpad swelling. These experiments demonstrate that the granuloma T-lymphocyte population contains TDH-type effector cells. Establishment of an SEA-specific granuloma T-cell line will allow the study of the effector functions of the hitherto uncharacterized intralesional granuloma T lymphocyte.

Effect of chemotactins released by Staphylococcus aureus and Pseudomonas aeruginosa on the murine respiratory tract

Staphylococcus aureus, the Pseudomonas aeruginosa temperature-sensitive (ts) mutant A/10/25, and the P. aeruginosa parental wild type were aerosolized to C5-deficient mice, and the total number of polymorphonuclear leukocytes (PMN) recovered by lung lavage was determined 4 h after aerosol exposure. S. aureus induced a slight but significant recruitment of PMN, as compared with the effect of a saline aerosol. Both wild-type P. aeruginosa and the ts mutant induced a significant PMN recruitment of a magnitude ca. 180 times higher than that produced by S. aureus. Gentamicin-killed ts P. aeruginosa induced a PMN recruitment of a magnitude similar to that produced by live ts P. aeruginosa. Thorough washing of the bacteria, however, removed ca. 90% of the chemotactic activity. Exposure of the animals to a ts P. aeruginosa culture supernatant aerosol induced significant PMN recruitment into the lower airways. The same culture supernatants were chemotactic for mouse PMN in a dose-dependent fashion when tested in vitro in the absence of serum. Culture supernatants of S. aureus exhibited weak chemotactic activity in vitro and did not induce PMN recruitment in the lungs when aerosolized to DBA/2J mice. The results suggest that chemotactins released by P. aeruginosa may be an important virulence factor and play a significant role in lung tissue damage.