Macrophages In Idiopathic Pulmonary Fibrosis Research Articles

Antifibrotic effect of disulfiram on bleomycin-induced lung fibrosis in mice and its impact on macrophage infiltration

The accumulation of monocyte-derived macrophages in the lung tissue during inflammation is important for the pathogenesis of fibrotic lung disease. Deficiencies in chemokine receptors CCR2 and CCR5 and their ligands, which mediate monocyte/macrophage migration, ameliorate bleomycin (BLM)-induced lung fibrosis. Disulfiram (DSF), which is used to treat alcoholism because of its aldehyde dehydrogenase (ALDH)-inhibiting effect, inhibits monocyte/macrophage migration by inhibiting FROUNT, an intracellular regulator of CCR2/CCR5 signalling. Here, we investigated the antifibrotic effect of oral DSF administration in a mouse model of BLM-induced lung fibrosis, focusing on macrophage response and fibrosis progression. The direct inhibitory activity of DSF on monocyte migration was measured using the Boyden chamber assay and compared with that of DSF-related inhibitors with different FROUNT-inhibition activities. Quantitative PCR was used to determine the expression of fibrosis-promoting genes in the lung tissue. DSF significantly suppressed macrophage infiltration into lung tissues and attenuated BLM-induced lung fibrosis. DSF and its metabolites, diethyldithiocarbamate (DDC) and copper diethyldithiocarbamate (Cu(DDC)2), inhibited monocyte migration toward the culture supernatant of primary mouse lung cells mainly comprising CCL2, whereas cyanamide, another ALDH inhibitor, did not. DSF, with higher inhibitory activity against FROUNT than DDC and Cu(DDC)2, inhibited monocyte migration most strongly. In BLM-induced fibrotic lung tissues, profibrotic factors were highly expressed but were reduced by DSF treatment. These results suggest DSF inhibits macrophage infiltration, which might be attributed to its inhibitory effect on FROUNT, and attenuates BLM-induced lung fibrosis. In addition, multiplex immunofluorescence imaging revealed reduced infiltration of S100A4+ macrophages into the lungs in DSF-treated mice and high expression of FROUNT in S100A4+ macrophages in idiopathic pulmonary fibrosis (IPF). These findings underscore the potential of macrophage-targeted therapy with DSF as a promising drug repositioning approach for treating fibrotic lung diseases, including IPF.

Multiomic analysis of monocyte-derived alveolar macrophages in idiopathic pulmonary fibrosis

BackgroundMonocyte-derived alveolar macrophages (Mo_AMs) are increasingly recognised as potential pathogenic factors for idiopathic pulmonary fibrosis (IPF). While scRNAseq analysis has proven valuable in the transcriptome profiling of Mo_AMs, the integration analysis of multi-omics may provide additional dimensions of understanding of these cellular populations.MethodsWe performed multi-omics analysis on 116 scRNAseq, 119 bulkseq and five scATACseq lung tissue samples from IPF. We built a large-scale IPF scRNAseq atlas and conducted the Monocle 2/3 as well as the Cellchat to explore the developmental path and intercellular communication on Mo_AMs. We also reported the difference in metabolisms, tissue repair and phagocytosis between Mo_AMs and tissue-resident alveolar macrophages (TRMs). To determine whether Mo_AMs affected pulmonary function, we projected clinical phenotypes (FVC%pred) from the bulkseq dataset onto the scRNAseq atlas. Finally, we used scATATCseq to uncover the upstream regulatory mechanisms and determine key drivers in Mo_AMs.ResultsWe identified three Mo_AMs clusters and the trajectory analysis further validated the origin of these clusters. Moreover, via the Cellchat analysis, the CXCL12/CXCR4 axis was found to be involved in the molecular basis of reciprocal interactions between Mo_AMs and fibroblasts through the activation of the ERK pathway in Mo_AMs. SPP1_RecMacs (RecMacs, recruited macrophages) were higher in the low-FVC group than in the high-FVC group. Specifically, compared with TRMs, the functions of lipid and energetic metabolism as well as tissue repair were higher in Mo_AMs than TRMs. But, TRMs may have higher level of phagocytosis than TRMs. SPIB (PU.1), JUNB, JUND, BACH2, FOSL2, and SMARCC1 showed stronger association with open chromatin of Mo_AMs than TRMs. Significant upregulated expression and deep chromatin accessibility of APOE were observed in both SPP1_RecMacs and TRMs.ConclusionThrough trajectory analysis, it was confirmed that SPP1_RecMacs derived from Monocytes. Besides, Mo_AMs may influence FVC% pred and aggravate pulmonary fibrosis through the communication with fibroblasts. Furthermore, distinctive transcriptional regulators between Mo_AMs and TRMs implied that they may depend on different upstream regulatory mechanisms. Overall, this work provides a global overview of how Mo_AMs govern IPF and also helps determine better approaches and intervention therapies.

Platelet Activating Factor Receptor and Intercellular Adhesion Molecule-1 Expression Increases in the Small Airway Epithelium and Parenchyma of Patients with Idiopathic Pulmonary Fibrosis: Implications for Microbial Pathogenesis.

Background: Idiopathic pulmonary fibrosis (IPF) is an irreversible lung fibrotic disorder of unknown cause. It has been reported that bacterial and viral co-infections exacerbate disease pathogenesis. These pathogens use adhesion molecules such as platelet activating factor receptor (PAFR) and intercellular adhesion molecule-1 (ICAM-1) to gain cellular entry, causing infections. Methods: Immunohistochemical staining was carried out for lung resections from IPF patients (n = 11) and normal controls (n = 12). The quantification of PAFR and ICAM-1 expression is presented as a percentage in the small airway epithelium. Also, type 2 pneumocytes and alveolar macrophages were counted as cells per mm2 of the parenchymal area and presented as a percentage. All image analysis was done using Image Pro Plus 7.0 software. Results: PAFR expression significantly increased in the small airway epithelium (p < 0.0001), type 2 pneumocytes (p < 0.0001) and alveolar macrophages (p < 0.0001) compared to normal controls. Similar trend was observed for ICAM-1 expression in the small airway epithelium (p < 0.0001), type 2 pneumocytes (p < 0.0001) and alveolar macrophages (p < 0.0001) compared to normal controls. Furthermore, the proportion of positively expressed type 2 pneumocytes and alveolar macrophages was higher in IPF than in normal control. Conclusions: This is the first study to show PAFR and ICAM-1 expression in small airway epithelium, type 2 pneumocytes and alveolar macrophages in IPF. These findings could help intervene microbial impact and facilitate management of disease pathogenesis.

Mast-cell expressed membrane protein-1 is expressed in classical monocytes and alveolar macrophages in idiopathic pulmonary fibrosis and regulates cell chemotaxis, adhesion, and migration in a TGFβ-dependent manner.

Mast-cell expressed membrane protein-1 (MCEMP1) is higher in patients with idiopathic pulmonary fibrosis (IPF) with an increased risk of death. Here we aimed to establish the mechanistic role of MCEMP1 in pulmonary fibrosis. We identified increased MCEMP1 expression in classical monocytes and alveolar macrophages in IPF compared with controls. MCEMP1 is upregulated by transforming growth factor beta (TGFβ) at the mRNA and protein levels in monocytic leukemia THP-1 cells. TGFβ-mediated MCEMP1 upregulation results from the cooperation of SMAD3 and SP1 via concomitant binding to SMAD3/SP1 cis-regulatory elements within the MCEMP1 promoter. We also found that MCEMP1 regulates TGFβ-mediated monocyte chemotaxis, adhesion, and migration. Our results suggest that MCEMP1 may regulate the migration and transition of monocytes to monocyte-derived alveolar macrophages during pulmonary fibrosis development and progression.NEW & NOTEWORTHY MCEMP1 is highly expressed in circulating classical monocytes and alveolar macrophages in IPF, is regulated by TGFβ, and participates in the chemotaxis, adhesion, and migration of circulating monocytes by modulating the effect of TGFβ in RHO activity.

ErbB4 promotes M2 activation of macrophages in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is the most common and fatal diffuse fibrotic lung disease accompanied by macrophage M2 activation. ErbB4 is involved in and affects the process of inflammation. In this study, we determined that the mRNA level and protein expression of ErbB4 and M2 cytokine members were increased in the serum of IPF patients. In mouse alveolar macrophage MH-S cells, after knocking down ErbB4 by siRNA, the mRNA level and protein expression of M2 activator induced by interleukin (IL)-4 were decreased compared with the control group. Activating by ErbB4 agonist neuromodulatory protein (NRG)-1, IL-4-induced M2 program was promoted. Mechanistically, treated with NRG-1 in MH-S cells, the phosphorylation level of Akt did not change, while the phosphorylation level of ERK increased. Using SCH772984 to inhibit ERK pathway, the increasing IL-4-induced M2 activation by NRG-1 was inhibited, and the high level of M2 activator protein expression and mRNA expression was restored. Collectively, our data support that ErbB4 and M2 programs are implicated in IPF, and ErbB4 participates in the regulation of M2 activation induced by IL-4 through the ERK pathway.

Macrophage Implication in IPF: Updates on Immune, Epigenetic, and Metabolic Pathways.

Idiopathic pulmonary fibrosis (IPF) is a lethal interstitial lung disease of unknown etiology with a poor prognosis. It is a chronic and progressive disease that has a distinct radiological and pathological pattern from common interstitial pneumonia. The use of immunosuppressive medication was shown to be completely ineffective in clinical trials, resulting in years of neglect of the immune component. However, recent developments in fundamental and translational science demonstrate that immune cells play a significant regulatory role in IPF, and macrophages appear to be among the most crucial. These highly plastic cells generate multiple growth factors and mediators that highly affect the initiation and progression of IPF. In this review, we will provide an update on the role of macrophages in IPF through a systemic discussion of various regulatory mechanisms involving immune receptors, cytokines, metabolism, and epigenetics.

Plasticity towards Rigidity: A Macrophage Conundrum in Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive, chronic, and ultimately fatal diffuse parenchymal lung disease. The molecular mechanisms of fibrosis in IPF patients are not fully understood and there is a lack of effective treatments. For decades, different types of drugs such as immunosuppressants and antioxidants have been tested, usually with unsuccessful results. Although two antifibrotic drugs (Nintedanib and Pirfenidone) are approved and used for the treatment of IPF, side effects are common, and they only slow down disease progression without improving patients’ survival. Macrophages are central to lung homeostasis, wound healing, and injury. Depending on the stimulus in the microenvironment, macrophages may contribute to fibrosis, but also, they may play a role in the amelioration of fibrosis. In this review, we explore the role of macrophages in IPF in relation to the fibrotic processes, epithelial–mesenchymal transition (EMT), and their crosstalk with resident and recruited cells and we emphasized the importance of macrophages in finding new treatments.

High-Expressed Macrophage Scavenger Receptor 1 Predicts Severity Clinical Outcome in Transplant Patient in Idiopathic Pulmonary Fibrosis Disease.

Background Lung transplantation has been performed worldwide and admitted as an effective treatment for patients with various end-stage lung diseases. However, limit reliable clinical indicators exist to identify patients at high risk for allograft failure in lung transplant recipients. The recent advances in the knowledge of immunological aspects of the pulmonary diseases, for that innate macrophage activation, are induced by pathogen or pathogen-derived molecules and widely accepted as the critical evidence among the pathogenesis of lung inflammation and fibrosis. This study was aimed at evaluating the clinical significance of CD86- and macrophage scavenger receptor 1- (MSR1-) positive cells during the development of idiopathic pulmonary fibrosis (IPF) and pulmonary arterial hypertension (PAH), and their potential roles in the prediction of the outcomes after lung transplantation were examined. Methods Tissues from lung transplantation for 37 IPF and 15 PAH patients from the Department of Cardiothoracic Surgery in Wuxi People's Hospital from December 2015 to December 2016 were analyzed by immunohistochemistry (IHC) for detecting the expression and CD86 and MSR1 and correlated with clinical events after lung transplantation. Results IHC results showed that the expression of MSR1, IL-13, and arginase-1 (Arg1) but not CD86 in the lung section of IPF patients was dramatically enhanced when compared with that of PAH patients. The expression of MSR1, IL-13, and Arg1 but not CD86 in the lung from IPF patients with smoking was significantly increased when compared with that from nonsmoking subjects. In addition, the expression of MSR1-positive cells in IPF subjects with Klebsiella pneumoniae infection was dramatically enhanced than that in noninfection subjects. MSR1-positive macrophages were negatively associated with FEV1 and with FVC but not associated with TLC and with TLCO. However, CD86-positive macrophages were not significantly associated with the above lung function-related factors. Furthermore, MSR1 had a higher area under the ROC curve (AUC) than CD86 for IPF diagnosis. Survival analysis indicated that high levels of MSR1-positive macrophages had a worse prognostic effect for IPF patients with lung transplantation. Conclusion Our study indicates the clinical significance of Klebsiella pneumoniae infection-related MSR1-positive cells in IPF progression, and it could be a prognostic marker in IPF after the lung transplant; development strategies to reduce the expression of MSR1-positive macrophages in IPF may be beneficial for the lung transplant.

Accumulation of damaged mitochondria in alveolar macrophages with reduced OXPHOS related gene expression in IPF

BackgroundImpaired mitochondria homeostasis and function are established hallmarks of aging and increasing evidence suggests a link with lung fibrosis. Mitochondria homeostasis may be also affected in alveolar macrophages (AMs) in idiopathic pulmonary fibrosis (IPF). In this study, we used bronchoalveolar lavage (BAL), a tool for both clinical and research purposes, and a rich source of AMs.MethodsBAL samples were examined from 52 patients with IPF and 19 healthy individuals. Measurements of mitochondria reactive oxygen species (mtROS), mitochondria morphology and related gene expression were performed. Additionally, autophagy and mitophagy levels were analysed.ResultsMitochondria in AMs from IPF patients had prominent morphological defects and impaired transcription paralleled to a significant reduction of mitochondria homeostasis regulators PINK1, PARK2 and NRF1. mtROS, was significantly higher in IPF and associated with reduced expression of mitochondria-encoded oxidative phosphorylation (OXPHOS) genes. Age and decline in lung function correlated with higher mtROS levels. Augmentation of damaged, oxidised mitochondria in IPF AMs however was not coupled to increased macroautophagy and mitophagy, central processes in the maintenance of healthy mitochondria levels.ConclusionOur results suggest a perturbation of mitochondria homeostasis in alveolar macrophages in IPF.

Ironing Out the Roles of Macrophages in Idiopathic Pulmonary Fibrosis.

Ironing Out the Roles of Macrophages in Idiopathic Pulmonary Fibrosis.

Collagen morphology influences macrophage shape and marker expression in vitro

Fibrosis is a process in which an accumulation of extracellular matrix (ECM) leads to an impaired function of the affected organ. Pulmonary fibrosis is the end-stage of several lung diseases, characterized by scarring of the lungs. Although macrophages are known to be important players in ECM homeostasis, their ability to respond to fibrosis-related morphological and mechanical changes of the ECM is relatively unexplored. In this study we aimed to elucidate the effect of ECM stiffness and morphology on macrophage polarization, by using a collagen type I-based in vitro system. Collagen morphology, but not stiffness, affected the relative expression of CD206 (the mannose receptor) and Ym1 (a murine marker of pro-healing M2 macrophages). Higher expression of Ym1 was found when macrophages were cultured on fibrous collagen. Globular collagen led to higher expression of CD206, a marker known to be upregulated on alveolar macrophages in idiopathic pulmonary fibrosis. Moreover, macrophages exhibited distinct differences in shape with actin-rich protrusions on fibrous collagen and more filopodia on globular collagen. In addition to these cytoskeletal changes, transmigration was higher when macrophages were cultured on fibrous collagen. Together these findings indicate that macrophages are sensitive to collagen morphology, responding with subtle changes in marker expression, shape and behavior rather than a complete polarization switch. This study emphasizes the complex interaction between macrophages and their surroundings, and the need for further exploration of both mechanical and morphological aspects.

Effect of an immunotoxin to folate receptor β on bleomycin-induced experimental pulmonary fibrosis

It has been suggested that alveolar and interstitial macrophages play a key role in the pathogenesis of idiopathic pulmonary fibrosis (IPF) by producing proinflammatory and/or fibrogenic cytokines. We showed that inflammatory macrophages expressed folate receptor beta (FRbeta) while resident macrophages in normal tissues expressed no or low levels of FRbeta. In the present study, we examined the distribution of FRbeta-expressing macrophages in the lungs of patients with usual idiopathic pulmonary fibrosis (UIP) and mice with bleomycin-induced pulmonary fibrosis (PF) and tested whether the depletion of FRbeta-expressing macrophages could suppress bleomycin-induced PF in mice. Immunostaining with anti-human or -mouse FRbeta monoclonal antibody (mAb) revealed that FRbeta-expressing macrophages were present predominantly in fibrotic areas of the lungs of patients with UIP and mice with bleomycin-induced PF. Intranasal administration of a recombinant immunotoxin, consisting of immunoglobulin heavy and light chain Fv portions of an anti-mouse FRbeta mAb and truncated Pseudomonas exotoxin A, increased survival significantly and reduced levels of total hydroxyproline and fibrosis in bleomycin-induced PF. In immunohistochemical analysis, decreased numbers of tumour necrosis factor-alpha-, chemokines CCL2- and CCL12-producing cells were observed in the immunotoxin-treated group. These findings suggest a pathogenic role of FRbeta-expressing macrophages in IPF. Thus, targeting FRbeta-expressing macrophages may be a promising treatment of IPF.

Quantitative evaluation of gene expression of IL-1 beta and IL-1 receptor antagonist (IL-1ra) from alveolar macrophages in idiopathic pulmonary fibrosis (IPF) and sarcoidosis

Our previous studies demonstrated the concomitant release of IL-1 and IL-1ra in the culture supernatants of alveolar macrophages in both healthy subjects and patients with interstitial lung diseases. IL-1ra was decreased in healthy smokers (HS), IPF, and sarcoidosis, compared to healthy nonsmokers (HNS), although an increase in IL-1 release could not be detected. In this study, we examined whether such findings could be found at the gene level, or reflect posttranscriptional regulation in patients with IPF (n = 8), sarcoidosis (n = 7), healthy smokers (n = 6) and healthy nonsmokers (n = 5). The expression of IL-1 beta, IL-1ra and a house keeping gene (glucose 6 phosphate dehydrogenase: G6PD) was investigated using reverse transcription polymerase chain reaction (RT-PCR). After RT-PCR, analysis and quantification of PCR products were performed by high-performance liquid chromatography. We used 26 cycle for IL-1 beta and IL-ra mRNA and 29 for G6PD, because amplification of mRNA was in the exponential phase on that cycles, respectively. The results were expressed as the ratio of each mRNA to G6PD mRNA. IL-1ra/G6PD ratio in patients with IPF and sarcoidosis, was lower than that in HNS. On the other hand, IL-1 beta/G6PD ratio was similar in all groups. IL-1ra/IL-1 beta ratio was decreased in patients with IPF and sarcoidosis, compared to HNS. These results suggest that decreased expression of IL-1ra gene may contribute to the development of chronic low grade inflammation of the lung.

Lipoic Acid Suppression of Neutrophil Respiratory Burst: Effect of NADPH

Lipoic acid (LA) and its reduced product dihydrolipoic acid (DHLA) are potent antioxidants with capacity to scavenge reactive oxygen species (ROS) and recycle endogenous antioxidants. LA may increase cellular glutathione (GSH), an antioxidant lacking in the lung's epithelial lining fluid in lung disorders such as idiopathic pulmonary fibrosis (IPF). Neutrophils (PMN) are key innate responders and are pivotal in clearing bacterial infection, therefore it is crucial to understand the impact LA may have on their function. Circulating neutrophils were isolated from healthy volunteers and pretreated with LA or diluent. Cells were subsequently activated with phorbol 12-myristate 13-acetate (PMA, 100 ng/ml) to induce ROS production. SOD-inhibitable reduction of acetylated cytochrome c demonstrated the PMA-dependent respiratory burst was suppressed by LA. Oxygen consumption also was diminished when PMA-stimulated cells were pretreated with LA. PMN respiratory burst was partially restored by addition of NADPH but not other pyridine nucleotides. LA did not inhibit glucose-6-phosphate dehydrogenase activity of PMN. These data together suggest that the reduction of LA to DHLA using cellular NADPH may limit the capacity of the PMN NADPH oxidase to produce superoxide. Further studies will be required to determine if LA can diminish excessive superoxide produced by PMN and/or alveolar macrophages in IPF or relevant disease models in vivo.

Decreased expression of haem oxygenase-1 by alveolar macrophages in idiopathic pulmonary fibrosis

Haem oxygenase (HO)-1 is an oxidative stress responsive protein that may be involved in the pathogenesis of interstitial lung disease. HO-1 expression in alveolar macrophages from bronchoalveolar lavage was investigated in 24 patients with idiopathic pulmonary fibrosis (IPF), 16 with sarcoidosis, 14 with hypersensitivity pneumonitis (HP) and 13 controls. Using immunocytochemistry, HO-1 expression in macrophages was scored semiquantitatively from 0-3 according to increasing intensity. The mean score of 100 macrophages was calculated. Macrophages were cultured and levels of interleukin (IL)-12 and IL-18 in the culture supernatants were measured by ELISA. The mean score of HO-1 was significantly lower in IPF (67) than in sarcoidosis (105), HP (106) or controls (106). There was no significant difference between sarcoidosis, HP and controls. The score of HO-1 correlated positively with the lymphocyte percentage in sarcoidosis and HP. Positive correlations were found between the score of HO-1 and the release of IL-12 and IL-18 by macrophages in IPF. The expression of haem oxygenase-1, a critical defender against oxidative stress, is decreased in macrophages of idiopathic pulmonary fibrosis patients compared with those with granulomatous lung disorders. This supports the hypothesis of an oxidant-antioxidant imbalance in the pathogenesis of idiopathic pulmonary fibrosis.

Reduced expression of cyclooxygenase (COX) in idiopathic pulmonary fibrosis and sarcoidosis.

To test the hypothesis that cyclooxygenase (COX)-1 or COX-2 expression is defective in lungs in idiopathic pulmonary fibrosis (IPF) and to characterize the cellular distribution. IPF is a progressive inflammatory lung disorder with an adverse prognosis. Previous work has shown that prostaglandin E2 (PGE2) regulates collagen deposition and fibroblast proliferation and a defect in COX regulation may contribute to the fibrosis that occurs in IPF. Immunohistochemistry was utilized to determine COX immunoreactivity in lung sections from 25 IPF, six sarcoidosis and 14 control subjects. COX-1 and COX-2 expression in bronchiolar epithelial cells was significantly lower in IPF and sarcoidosis than in controls. No significant difference was found in COX-2 expression between macrophages in IPF and control sections, but COX-2 was reduced in macrophages in sarcoidosis compared with controls. These studies confirm COX-2 loss in bronchial epithelial cells but not macrophages in IPF, and show for the first time reduced constitutive COX-1 expression in epithelial cells and macrophages. Similar abnormalities were observed in sarcoidosis.

Increased expression of the interleukin-8 gene by alveolar macrophages in idiopathic pulmonary fibrosis. A potential mechanism for the recruitment and activation of neutrophils in lung fibrosis.

Neutrophil migration into the airspaces of the lung is thought to contribute to the alveolar damage and subsequent fibrosis in idiopathic pulmonary fibrosis (IPF). Interleukin 8 (IL-8), a monocyte- and macrophage-derived cytokine, displays potent chemotactic and activating properties towards neutrophils and thus may contribute to the pathogenesis of IPF. The objective of this investigation was to quantify the spontaneous expression of IL-8 transcripts by alveolar macrophages from normal healthy volunteers and individuals with IPF. A quantitative assay employing reverse transcription of mRNA and the polymerase chain reaction was utilized. The level of IL-8 mRNA in alveolar macrophages was found to be significantly elevated in individuals with lone IPF or with lung fibrosis associated with connective tissue disorders compared to normal healthy controls. Moreover, the level of IL-8 mRNA in the 23 individuals with IPF correlated with the number of neutrophils per milliliter in their bronchoalveolar lavage (BAL) and with the degree of disease severity. In addition, the level of IL-8 protein in BAL was found to reflect the pattern of IL-8 mRNA expression by alveolar macrophages. These data suggest that IL-8 derived from alveolar macrophages may significantly contribute to neutrophil involvement in the pathogenesis of IPF.

Presence of Platelet-derived Growth Factor in Normal and Fibrotic Lung Is Specifically Associated with Interstitial Macrophages, While Both Interstitial Macrophages and Alveolar Epithelial Cells Express the c-sis Proto-oncogene

Normal lung structure is maintained by the presence of mesenchymal cells and their extracellular matrix products. The slow normal turnover of these cells is disrupted in fibrotic disorders, resulting in the in situ accumulation of mesenchymal cells and their extracellular matrix leading to a progressive alveolar wall thickening. Idiopathic pulmonary fibrosis (IPF) is a chronic fibrotic disorder of the lung characterized by a diffuse interstitial and intra-alveolar inflammation dominated by macrophages and polymorphonuclear neutrophils. Evaluation of alveolar macrophages (AM) obtained by bronchoalveolar lavage has previously shown that AM from normal individuals spontaneously release small amounts of platelet-derived growth factor (PDGF), a chemotactic and growth factor for mesenchymal cells, whereas AM from IPF patients spontaneously release increased amounts of biologically active PDGF, suggesting its involvement in mesenchymal cell accumulation. However, other cells such as endothelial cells and vascular smooth muscle cells can also release PDGF in vitro. In order to specify PDGF location in lung parenchyma, open lung biopsies from normal individuals and IPF patients were examined by immunohistochemistry using an anti-PDGF antibody and by in situ hybridization using PDGF A-chain and B-chain gene probes. In normal as well as in fibrotic lung, PDGF was only present in relation with interstitial macrophages but not with any other inflammatory cells or mesenchymal cells. Furthermore, the percentage of PDGF-positive macrophages in IPF was 3-fold increased in comparison to normal lung. In addition, the percentage of PDGF-positive macrophages was the same in fibrotic and nonfibrotic areas of IPF lungs.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar macrophages in idiopathic pulmonary fibrosis display a more monocyte-like immunophenotype and an increased release of free oxygen radicals

Bronchoalveolar lavage (BAL) was performed in 13 patients with idiopathic pulmonary fibrosis (IPF) and in 10 control subjects. Free oxygen radical (FOR) production of alveolar macrophages (AM) and of blood monocytes was measured by luminol-dependent chemiluminescence (LDCL) without and after stimulation with zymosan A. We confirmed earlier studies that alveolar macrophages of IPF patients display a significantly elevated release of FOR under basic and under stimulated conditions. In contrast to alveolar macrophages, blood monocytes did not reveal altered LDCL in IPF. This indicates that the functional properties for augmented FOR release by IPF alveolar macrophages are acquired in the lungs and not in the peripheral circulation. To elucidate the possible mechanisms leading to the augmented LDCL response, immunophenotyping of alveolar macrophages was carried out. A panel of new monoclonal antibodies of the Ki-M-series, discriminating differentiation stages of monocyte/macrophage subpopulations, served for immunocytochemical staining. In IPF patients distribution of Ki-M2, Ki-M3, Ki-M6 and Ki-M8 positive AM demonstrated an increased proportion of alveolar macrophages expressing a more monocyte-like immunophenotype. Normally, monocytes as precursors of AM reveal a markedly stronger LDCL than alveolar macrophages themselves. Therefore, it seems likely that the increased LDCL of alveolar macrophages in IPF is due to the higher proportion of more immature monocyte-like cells in the alveoli of these patients.