Evaluation of alveolar macrophages in normals and individuals with active pulmonary sarcoidosis for the spontaneous expression of the interleukin-1 beta gene

The NLRP3 inflammasome pathway is activated in sarcoidosis and involved in granuloma formation

Sarcoidosis is a disease characterised by granuloma formation. There is an unmet need for new treatment strategies beyond corticosteroids. The NLRP3 inflammasome pathway is expressed in innate immune cells and senses danger signals to elicit inflammatory interleukin (IL)-1β; it has recently become a druggable target. This prompted us to test the role of the NLRP3 inflammasome and IL-1β pathway in granuloma formation and sarcoidosis.

19 sarcoid patients and 19 healthy volunteers were recruited into this pilot study. NLRP3 inflammasome activity was measured in bronchoalveolar lavage (BAL) cells and lung and skin biopsies using immunohistochemistry, Western blot, reverse-transcriptase PCR and ELISA. For in vivo experiments we used the trehalose 6,6′-dimycolate-granuloma mouse model and evaluated lung granuloma burden in miR-223 knockout and NLRP3 knockout mice, as well as the treatment effects of MCC950 and anti-IL-1β antibody therapy.

We found strong upregulation of the NLRP3 inflammasome pathway, evidenced by expression of activated NLRP3 inflammasome components, including cleaved caspase-1 and IL-1β in lung granuloma, and increased IL-1β release of BAL cells from sarcoid patients compared to healthy volunteers (p=0.006). mRNA levels of miR-223, a micro-RNA downregulating NLRP3, were decreased and NLRP3 mRNA correspondingly increased in alveolar macrophages from sarcoid patients (p<0.005). NLRP3 knockout mice showed decreased and miR-223 knockout mice increased granuloma formation compared to wild-type mice. Pharmacological interference using NLRP3 pathway inhibitor MCC950 or an anti-IL-1β antibody resulted in reduced granuloma formation (p<0.02).

In conclusion, our data provide evidence of upregulated inflammasome and IL-1β pathway activation in sarcoidosis and suggest both as valid therapeutic targets.

Lung lymphocytes: origin, biological functions, and laboratory techniques for their study in immune-mediated pulmonary disorders

Different types of immunocompetent cells, including T lymphocytes and alveolar macrophages, account for pulmonary host defense. Taking advantage of the availability of the monoclonal antibody technique, cell culture facilities, pure recombinant cytokines, and molecular probes for their genes, in the last few years it has been possible to keenly study the different steps that lead to the compartmentalization of immune response in human lung. Furthermore, the immunological analysis of cells retrieved from bronchoalveolar lavage (BAL) allowed recognition of the importance of immune mechanisms in the evolution of immune-mediated pulmonary disorders. The purpose of this review is to summarize recent advances on the immunologic characterization of lung lymphocytes in health and disease. Following a brief description of the pathways through which the pulmonary lymphoid system contributes to removing potentially harmful inhaled antigenic materials, available laboratory techniques to evaluate the lymphoid component of the pulmonary immune system and their byproducts are discussed. These techniques cover methods for preparing lymphocytes from the BAL fluid and for characterizing lung lymphocytes both in cell suspensions and pulmonary tissue biopsies. Other sections of this review describe the techniques for measuring the immunologic effector functions of lung lymphocytes. We also provide the reader with a flavor of the molecular biology methods used to characterize lymphocytes in the pulmonary microenvironment. The final sections of the review article highlight the pathogenetic role envisaged for lymphoid cells in pulmonary disease states and emphasize the importance of the BAL analysis in the clinical management of the most relevant immune-mediated lung disease.

Structural diversity in the 5'-untranslated region of cytokine-stimulated human inducible nitric oxide synthase mRNA

Inducible nitric oxide synthase, the critical enzyme responsible for the enhanced synthesis of nitric oxide in inflammatory states, is widely expressed in mammalian cells. To evaluate potential regulatory roles of the 5'-untranslated region (UTR) in the human inducible nitric oxide synthase gene, the transcription initiation sites and structure of the 5'-UTR of human inducible nitric oxide synthase were examined. Freshly isolated human alveolar macrophages, bronchial epithelial cells, and several types of cultured cells were evaluated following stimulation with cytokines (i.e. interferon-gamma, interleukin-1 beta, tumor necrosis factor-alpha, and interleukin-6). The mRNA was analyzed by reverse transcription-polymerase chain reaction. Northern analysis, and 5'-rapid amplification of cDNA ends. Despite the presence of a TATA box in the promoter region, multiple transcription initiation sites were observed, some extending several hundred base pairs upstream from the main TATA-directed initiation site. Alternative splicing in the 5'-UTR of human inducible nitric oxide synthase mRNA resulted in further diversity. The TATA-independent inducible nitric oxide synthase mRNA transcripts were up-regulated by cytokines. The long and complex 5'-UTRs contain eight partially overlapping open reading frames upstream of the putative inducible nitric oxide synthase ATG, which may have an important role in translational regulation of human inducible nitric oxide synthase mRNA.

Interleukin-1 receptor antagonist expression in sarcoidosis

Sarcoidosis is a systemic granulomatous disease with a marked propensity for involvement of the pulmonary parenchyma and thoracic lymphatic system. This granulomatous process is characterized by aggregations of mononuclear cells, multinucleated giant cells, and variable degrees of fibrosis. The agent(s) responsible for the initiation of the inflammatory granulomatous process remain unknown. Interleukin-1 beta (IL-1) is a cytokine that has been shown to possess potent proinflammatory properties and is likely to play a role in mediating many of the immunopathologic events observed in sarcoidosis. Despite the degree of granulomatous inflammation, both the pulmonary and systemic pathogenic changes associated with sarcoidosis have a remarkable propensity for spontaneous resolution. The interleukin-1 receptor antagonist (IRAP), an endogenous inhibitor of IL-1 bioactivity, may have a critical role as an in vivo immunomodulator of IL-1-dependent granulomatous inflammation of sarcoidosis. In this study we demonstrate constitutive expression of IRAP mRNA and antigen from bronchoalveolar lavage fluid cells and cell-free fluid, respectively, obtained from both normal subjects and patients with sarcoidosis. However, immunolocalization of IRAP was found to be significantly localized to the sarcoid granuloma as compared with the uninvolved lung interstitium. Our findings indicate that IRAP expression is compartmentalized (granuloma) within the interstitium of patients with sarcoidosis. Thus, IRAP may function as an important in vivo immunomodulator of granulomatous inflammation.

Inhibitory effects of inhaled flunisolide on inflammatory functions of alveolar macrophages

We have studied 15 patients with slight or moderate bronchial obstruction, all of whom were being treated by inhalation of the beta-mimetic fenoterol 4 x 400 micrograms/day, and 7 of whom were also receiving inhaled flunisolide 2 x 500 micrograms/day. The therapy had been given for longer than 1 month in each case. Bronchoscopy and bronchoalveolar lavage (BAL) was done for diagnosis or follow up of bronchial diseases. None of the patients showed signs of any interstitial lung disease. Conditioned culture supernatants were produced by cultivating alveolar macrophages (AM) for 24 h using standard conditions. To detect all the biological effects both of IL-1 alpha and IL-1 beta in the culture supernatants a modification of the standard mouse IL-1 thymocyte bioassay was used. The TNF concentration in culture supernatants was measured by ELISA. Free oxygen radical release by alveolar macrophages was determined by the detection of chemiluminescence. Both IL-1 and TNF production were significantly lower in patients receiving fenoterol plus flunisolide than in patients on fenoterol alone. In contrast, no difference could be observed in the release of free oxygen radicals from alveolar macrophages. Thus, for the first time an ex vivo study has revealed an interrelation between inhaled glucocorticoid therapy and inhibition of important mediators of inflammatory processes in the lower respiratory tract.

Increased secretion of tumor necrosis factor-alpha, interleukin-1-beta, and interleukin-6 by alveolar macrophages from patients with sarcoidosis

BACKGROUND

Alveolar macrophages from patients with sarcoidosis were analyzed for their ability to secrete tumor necrosis factor-alpha (TNF-alpha), interleukin-1-beta (IL-1-beta), and interleukin-6 (IL-6).

RESULTS

Constitutive release of all three monokines in these patients was concomitantly increased in the active state of disease in comparison with inactive sarcoidosis or healthy control subjects. Alveolar macrophages from patients with inactive sarcoidosis compared with cells from healthy subjects showed increased spontaneous secretion of TNF-alpha and IL-6 only, whereas the constitutive release of IL-1-beta was similar as in healthy volunteers. In vitro stimulation of alveolar macrophages from healthy control subjects with lipopolysaccharide or pokeweed mitogen led to a time- and dose-dependent enhanced secretion of TNF-alpha, IL-1-beta, and IL-6. In a similar manner, with corresponding cells from patients with sarcoidosis the secretion of all three cytokines could be further increased by stimulation with lipopolysaccharide or pokeweed mitogen.

CONCLUSIONS

The data presented indicate that an increased release of TNF-alpha, IL-1-beta, and IL-6 correlates to disease activity and may play a critical part in the pathogenesis of sarcoidosis.

Localization of intestinal interleukin 1 activity and protein and gene expression to lamina propria cells

BACKGROUND

Interleukin 1 (IL-1) is a key mediator of bowel inflammation, but there is limited knowledge about the amount and site of production of this cytokine in the gastrointestinal tract under physiological or pathological conditions.

METHODS

Epithelial and lamina propria mononuclear cells were isolated from control, and Crohn's disease- and ulcerative colitis-involved mucosa to investigate the capacity of these cells to generate IL-1 bioactivity, IL-1 alpha and IL-1 beta immunoreactivity, and gene expression.

RESULTS

Control lamina propria mononuclear cells produced substantial amounts of IL-1 alpha and IL-1 beta, which increased dramatically when inflammatory bowel disease cells were used. Epithelial cells from control, Crohn's disease, and ulcerative colitis intestine displayed no IL-1 bioactivity or immunoreactivity. Lamina propria mononuclear cells contained moderate to large quantities of IL-1 alpha and IL-1 beta messenger RNA (mRNA), respectively, whereas epithelial cells had none. The absence of IL-1 transcripts in epithelial cells was selective, because mRNA for HLA-DR antigens was present in control and inflammatory bowel disease cells.

CONCLUSIONS

In normal and inflamed human intestine there is a distinct compartmentalization of IL-1, as mononuclear but not epithelial cells generate this cytokine. The high levels of IL-1 in inflammatory bowel disease may explain several of its local and systemic manifestations, and blockade by specific antagonists could have important therapeutic effects.

Production of cytokines in sarcoid lymph nodes: preferential expression of interleukin-1 beta and interferon-gamma genes

Sarcoidosis is a chronic granulomatous disease that may be considered to be a human model for the delayed-type hypersensitivity reaction. The expression of cytokine genes in organs displaying sarcoid granulomas was analyzed by in situ hybridization with several cytokine probes using biopsies from 11 sarcoid lymph nodes. We detected cells expressing interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), IL-6, IL-2, and interferon-gamma (IFN-gamma) genes in all lymph nodes. The major finding of this study was that cytokine genes are independently expressed. Of the monokine genes, the IL-1 beta gene was preferentially expressed. The distribution of cells containing IL-1 beta mRNA was characterized by their amalgamation in clusters inside sarcoid granulomas. Cells expressing the TNF-alpha gene were located exclusively inside granulomas and were always scattered. Cells expressing the IL-6 gene or the IL-1 alpha gene were found scattered inside sarcoid granulomas and in the residual lymphoid tissue. The number of cells expressing the IL-1 beta gene was significantly higher than that of cells expressing TNF-alpha gene (P = .001), IL-6 gene (P = .007), or IL-1 alpha gene (P less than .001). Of the cells expressing lymphokine genes, those expressing the IFN-gamma gene were 31.9 (+/- 7.6) times more frequent than those expressing the IL-2 gene (P less than .001). Cells containing IFN-gamma mRNA were detected mainly inside sarcoid granulomas, whereas cells containing IL-2 mRNA were randomly distributed. These results show that each monokine gene or lymphokine gene can be independently expressed in vivo. The high expression level of the IL-1 beta gene and the IFN-gamma gene inside granulomas may be specific to delayed-type hypersensitivity immune reactions.

Detection of endogenous cytokines in sera or in lymph nodes obtained from patients with sarcoidosis

To investigate the possible role of endogenous cytokines in the immunopathogenesis of sarcoidosis, a study of cytokines in lymph nodes obtained from patients with active pulmonary sarcoidosis was carried out using immunoperoxidase staining and radioimmunoassays (RIA). Cells stained for interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha), which appeared to be CD3+ cells and CD14+ cells, respectively, were seen scattered around granulomas. In contrast, cells positive for interleukin-1 beta (IL-1 beta) were located in CD11c+ cells within granulomas. Lymph nodes of patients with sarcoidosis contained significantly higher amounts of IFN-gamma, TNF-alpha and IL-1 beta than control lymph nodes. The levels of IFN-gamma and TNF-alpha in extracts of lymph nodes were correlated with the histological status of the granulomas. IFN-gamma was detected in all stages, while the highest level of TNF-alpha was obtained from lymph nodes containing many active granulomas. The level of serum IFN-gamma was always lower than in lymph node extract and correlated significantly with either serum angiotensin-converting enzyme or serum lysozyme. Patients with positive gallium-67 uptake or bilateral hilar lymphadenopathy had high levels of either serum IFN-gamma or lysozyme. These results suggest that quantitative analyses of IFN-gamma and TNF-alpha in sera and lymph nodes may serve to elucidate the pathophysiology of sarcoidosis.

Increased levels of serum interferon-gamma in pulmonary sarcoidosis and relationship with response to corticosteroid therapy

The aim of this study was to evaluate serum levels of the lymphokine interferon-gamma (IFNg) in patients with chronic pulmonary sarcoidosis, and to investigate its value as a predictive marker of clinical response to corticosteroid therapy. Twenty-five patients and 28 age-matched control subjects were studied. All the patients had parenchymal shadows (Stage II or Stage III) and none had clinical evidence of extrathoracic disease. Before therapy, serum IFNg levels were significantly higher in the patient group (p less than 0.001), and 20 (80%) had values above the normal range. After oral treatment with corticosteroids for a median 13 months (range, 3 to 49 months) the levels decreased significantly (p less than 0.01). However, the falls were less pronounced in patients who had a better outcome in terms of achieving complete radiographic resolution and in those who improved in forced vital capacity by greater than or equal to 10%. The prognostic value of the pretreatment serum IFNg was explored, and a significant relationship was found between higher pretreatment levels and lower grades or radiographic abnormality assessed 3 yr after commencement of treatment (p less than 0.01). In addition, the patients who had cleared completely while receiving steroids and remained in remission had significantly higher pretreatment serum IFNg levels than did those with incomplete resolution of parenchymal shadows or radiographic relapses (p less than 0.05). We conclude that elevated levels of circulating IFNg are detectable in most untreated patients with Stage II/III pulmonary sarcoidosis and that patients with the highest levels appear to have a better chance of achieving complete resolution with corticosteroid therapy.

Effect of bronchoalveolar lavage fluid from patients with sarcoidosis or AIDS on interleukin 1 beta release from alveolar macrophages

We studied the effect of concentrated surfactant-depleted BALF from 8 normal subjects, 13 patients with sarcoidosis, and 13 patients with AIDS on IL1 beta release by human AM. Adherent target AM were exposed to concentrated BALF in the presence or absence of LPS (1 microgram/ml) for two hours. Control AM were unexposed to BALF. After an additional 24-hour incubation, AM supernatants were collected and measured for IL1 beta by ELISA. No spontaneous IL1 beta release occurred from unstimulated AM. One of the sarcoid-BALF and three of the AIDS-BALF samples induced a small amount of IL1 beta release from unstimulated AM. In LPS-stimulated AM, exposure to normal BALF did not significantly alter IL1 beta release compared to unexposed AM. Exposure to sarcoid-BALF significantly increased the release of IL1 beta, while exposure to AIDS-BALF significantly reduced the IL1 beta level in the AM supernatants. The latter effect was related to the higher mortality induced by AIDS-BALF in AM. These data show that release of IL1 beta from LPS-stimulated AM is modified by a short exposure to a sample of alveolar fluid from patients with lung disease.

Alveolar macrophages release an insulin-like growth factor I-type molecule

Human alveolar macrophages, when activated, release a progression-type growth factor for fibroblasts that signals "competent" fibroblasts to replicate. The present study demonstrates that this growth activity is an insulin-like growth factor I (IGF-I)-type molecule. Partial purification of medium conditioned by activated alveolar macrophages using ion exchange and gel filtration chromatography revealed an IGF-I molecule as detected by an anti-IGF-I polyclonal antibody and that the specific activity of the progression-type growth activity tracked with the amount of IGF-I present. In a serum-free complementation test, the increase in fibroblast proliferation by alveolar macrophage IGF-I was reduced in a dose-response manner with an anti-IGF-I monoclonal antibody. The alveolar macrophage IGF-I displaced 125I-IGF-I from its receptor in a binding assay utilizing human lung fibroblasts and it stimulated type I IGF receptors purified from human lung fibroblasts to phosphorylate a tyrosine-containing artificial substrate. In contrast to the 7.6-kD serum IGF-I, gel chromatography revealed that the alveolar macrophage IGF-I had an apparent molecular mass of 26 kD, similar to other tissue IGF-Is. Alveolar macrophages expressed IGF-I mRNA transcripts as detected by solution hybridization using a 32P-labeled riboprobe complementary to exons I-II-III of the IGF-I gene. In the context of the known functions of the family of IGF-I molecules in cell growth, IGF-I released by activated alveolar macrophages may play a role in acute and chronic inflammatory disorders.

Differential expression of the tumor necrosis factor/cachectin gene by blood and lung mononuclear phagocytes

Tumor necrosis factor (TNF), also called cachectin, is a mononuclear phagocyte-derived mediator with a broad range of biologic activities contributing to antineoplastic and antiviral defenses as well as mediating a variety of processes associated with acute and chronic inflammatory states, including endotoxin-induced shock. To evaluate the relative capacity of human tissue macrophages to produce this mediator, alveolar macrophages and blood monocytes from the same normal individuals were activated with lipopolysaccharide (LPS) and evaluated for TNF release and TNF mRNA transcript levels. Resting alveolar macrophages did not express TNF mRNA transcripts or release TNF. However, when activated, alveolar macrophages expressed TNF transcripts and synthesized and released TNF as evidenced by the presence of a 28 kDa mediator in LPS-activated alveolar macrophage supernatants that had cytotoxic activity for L-929 cells that was abrogated by anti-TNF antibodies and that coeluted with a pure TNF standard on a molecular sieve column. Interestingly, activated alveolar macrophages released severalfold more TNF than did autologous blood monocytes stimulated in a similar fashion and, in parallel, the alveolar macrophages expressed more TNF mRNA transcripts than activated blood monocytes. Thus, the ability to express the TNF gene and to release TNF apparently increases during maturation of blood monocytes into alveolar macrophages, suggesting that the release of TNF in the local milieu by activated tissue macrophages may be much more significant than the release of this mediator by circulating blood monocytes.

Interleukins in pulmonary sarcoidosis. Dissociative correlations of lung interleukins 1 and 2 with the intensity of alveolitis

To investigate whether interleukins are involved in the formation of alveolitis in pulmonary sarcoidosis, interleukin-1 (IL-1) production by LPS-stimulated alveolar macrophages (AM) and interleukin-2 (IL-2) production by PHA-stimulated lung and blood T-cells were determined in 35 untreated patients with pulmonary sarcoidosis. The amount of IL-1 produced by AM (BAL IL-1) was significantly increased in patients with pulmonary sarcoidosis compared with that in 18 control subjects. BAL IL-1 showed a significant positive correlation with the intensity of alveolitis assessed by the proportion of lymphocytes in bronchoalveolar lavage fluid (BALF) and the absolute number of lymphocytes per milliliter of BALF. However, the amount of IL-2 produced by lung T-cells (BALT IL-2) showed a significant negative correlation with the intensity of alveolitis. BALT IL-2 was significantly lower than the amount of IL-2 produced by blood T-cells (PBT IL-2). There was no correlation between PBT IL-2 and the intensity of alveolitis. These results suggest that IL-2 contributes to the formation and maintenance of alveolitis in pulmonary sarcoidosis, whereas IL-2 production by lung T-cells is suppressed to down-regulate the enhanced immune processes at the site of disease. The possibility that this hyporesponsiveness of lung T-cells to PHA has resulted from the modulation of the T3-T cell receptor complex remains to be determined.