Bleomycin stimulation of cytokine secretion by the human alveolar macrophage

Telomere Maintenance and the cGAS-STING Pathway in Cancer

Cancer cells exhibit the unique characteristics of high proliferation and aberrant DNA damage response, which prevents cancer therapy from effectively eliminating them. The machinery required for telomere maintenance, such as telomerase and the alternative lengthening of telomeres (ALT), enables cancer cells to proliferate indefinitely. In addition, the molecules in this system are involved in noncanonical pro-tumorigenic functions. Of these, the function of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway, which contains telomere-related molecules, is a well-known contributor to the tumor microenvironment (TME). This review summarizes the current knowledge of the role of telomerase and ALT in cancer regulation, with emphasis on their noncanonical roles beyond telomere maintenance. The components of the cGAS-STING pathway are summarized with respect to intercell communication in the TME. Elucidating the underlying functional connection between telomere-related molecules and TME regulation is important for the development of cancer therapeutics that target cancer-specific pathways in different contexts. Finally, strategies for designing new cancer therapies that target cancer cells and the TME are discussed.

Spred2-deficiency enhances the proliferation of lung epithelial cells and alleviates pulmonary fibrosis induced by bleomycin

The mitogen-activated protein kinase (MAPK) pathways are involved in many cellular processes, including the development of fibrosis. Here, we examined the role of Sprouty-related EVH-1-domain-containing protein (Spred) 2, a negative regulator of the MAPK-ERK pathway, in the development of bleomycin (BLM)-induced pulmonary fibrosis (PF). Compared to WT mice, Spred2^−/− mice developed milder PF with increased proliferation of bronchial epithelial cells. Spred2^−/− lung epithelial cells or MLE-12 cells treated with spred2 siRNA proliferated faster than control cells in vitro. Spred2^−/− and WT macrophages produced similar levels of TNFα and MCP-1 in response to BLM or lipopolysaccharide and myeloid cell-specific deletion of Spred2 in mice had no effect. Spred2^−/− fibroblasts proliferated faster and produced similar levels of MCP-1 compared to WT fibroblasts. Spred2 mRNA was almost exclusively detected in bronchial epithelial cells of naïve WT mice and it accumulated in approximately 50% of cells with a characteristic of Clara cells, 14 days after BLM treatment. These results suggest that Spred2 is involved in the regulation of tissue repair after BLM-induced lung injury and increased proliferation of lung bronchial cells in Spred2^−/− mice may contribute to faster tissue repair. Thus, Spred2 may present a new therapeutic target for the treatment of PF.

Amifostine Analog, DRDE-30, Attenuates Bleomycin-Induced Pulmonary Fibrosis in Mice

Bleomycin (BLM) is an effective curative option in the management of several malignancies including pleural effusions; but pulmonary toxicity, comprising of pneumonitis and fibrosis, poses challenge in its use as a front-line chemotherapeutic. Although Amifostine has been found to protect lungs from the toxic effects of radiation and BLM, its application is limited due to associated toxicity and unfavorable route of administration. Therefore, there is a need for selective, potent, and safe anti-fibrotic drugs. The current study was undertaken to assess the protective effects of DRDE-30, an analog of Amifostine, on BLM-induced lung injury in C57BL/6 mice. Whole body micro- computed tomography (CT) was used to non-invasively observe tissue damage, while broncheo-alveolar lavage fluid (BALF) and lung tissues were assessed for oxidative damage, inflammation and fibrosis. Changes in the lung density revealed by micro-CT suggested protection against BLM-induced lung injury by DRDE-30, which correlated well with changes in lung morphology and histopathology. DRDE-30 significantly blunted BLM-induced oxidative stress, inflammation and fibrosis in the lungs evidenced by reduced oxidative damage, endothelial barrier dysfunction, Myeloperoxidase (MPO) activity, pro-inflammatory cytokine release and protection of tissue architecture, that could be linked to enhanced anti-oxidant defense system and suppression of redox-sensitive pro-inflammatory signaling cascades. DRDE-30 decreased the BLM-induced augmentation in BALF TGF-β and lung hydroxyproline levels, as well as reduced the expression of the mesenchymal marker α-smooth muscle actin (α-SMA), suggesting the suppression of epithelial to mesenchymal transition (EMT) as one of its anti-fibrotic effects. The results demonstrate that the Amifostine analog, DRDE-30, ameliorates the oxidative injury and lung fibrosis induced by BLM and strengthen its potential use as an adjuvant in alleviating the side effects of BLM.

Induced Pluripotent Stem Cells Inhibit Bleomycin-Induced Pulmonary Fibrosis in Mice through Suppressing TGF-β1/Smad-Mediated Epithelial to Mesenchymal Transition

Pulmonary fibrosis is a progressive and irreversible fibrotic lung disorder with high mortality and few treatment options. Recently, induced pluripotent stem (iPS) cells have been considered as an ideal resource for stem cell-based therapy. Although, an earlier study demonstrated the therapeutic effect of iPS cells on pulmonary fibrosis, the exact mechanisms remain obscure. The present study investigated the effects of iPS cells on inflammatory responses, transforming growth factor (TGF)-β1 signaling pathway, and epithelial to mesenchymal transition (EMT) during bleomycin (BLM)-induced lung fibrosis. A single intratracheal instillation of BLM (5 mg/kg) was performed to induce pulmonary fibrosis in C57BL/6 mice. Then, iPS cells (c-Myc-free) were administrated intravenously at 24 h following BLM instillation. Three weeks after BLM administration, pulmonary fibrosis was evaluated. As expected, treatment with iPS cells significantly limited the pathological changes, edema, and collagen deposition in lung tissues of BLM-induced mice. Mechanically, treatment with iPS cells obviously repressed the expression ratios of matrix metalloproteinase-2 (MMP-2) to its tissue inhibitor -2 (TIMP-2) and MMP-9/TIMP-1 in BLM-induced pulmonary tissues. In addition, iPS cell administration remarkably suppressed BLM-induced up-regulation of pulmonary inflammatory mediators, including tumor necrosis factor-α, interleukin (IL)-1β, IL-6, inducible nitric oxide synthase, nitric oxide, cyclooxygenase-2 and prostaglandin E₂. We further demonstrated that transplantation of iPS cells markedly inhibited BLM-mediated activation of TGF-β1/Mothers against decapentaplegic homolog 2/3 (Smad2/3) and EMT in lung tissues through up-regulating epithelial marker E-cadherin and down-regulating mesenchymal markers including fibronectin, vimentin and α-smooth muscle actin. Moreover, in vitro, iPS cell-conditioned medium (iPSC-CM) profoundly inhibited TGF-β1-induced EMT signaling pathway in mouse alveolar epithelial type II cells (AECII). Collectively, our results suggest that transplantation of iPS cells could suppress inflammatory responses, TGF-β1/Smad2/3 pathway and EMT during the progression of BLM-induced pulmonary fibrosis, providing new useful clues regarding the mechanisms of iPS cells in the treatment for this disease.

17(R)-resolvin D1 ameliorates bleomycin-induced pulmonary fibrosis in mice

Idiopathic pulmonary fibrosis (IPF) is a destructive inflammatory disease with limited therapeutic options. Inflammation plays an integral role in the development of pulmonary fibrosis. Unresolved inflammatory responses can lead to substantial tissue injury, chronic inflammation, and fibrosis. The resolvins are a family of endogenous ω‐3 fatty acid derived‐lipid mediators of inflammation resolution. Resolvin D1 (RvD1) displays potent anti‐inflammatory, pro‐resolving activity, without causing immunosuppression. Its epimer, 17(R)‐resolvin D1 (17(R)‐RvD1), exhibits equivalent functionality to RvD1. In addition, 17(R)‐RvD1 is resistant to rapid inactivation by eicosanoid oxidoreductases. In the present study, we tested the hypothesis that 17(R)‐RvD1 can provide a therapeutic benefit in IPF by reducing inflammation and pulmonary fibrosis, while leaving the normal immune response intact. Mice were exposed to bleomycin (BLM) via micro‐osmotic pump to induce pulmonary fibrosis, and were then treated with 17(R)‐RvD1 or vehicle by intraperitoneal injection. Administration of 17(R)‐RvD1 from the start of BLM treatment attenuated neutrophil alveolar infiltration, lung collagen content, and Interleukin‐1β (IL‐1β), transforming growth factor‐β1 (TGF‐β1), connective tissue growth factor (CTGF), and type I collagen mRNA expression, along with subsequent reduction in histologically detectable fibrosis. The 17(R)‐RvD1‐induced infiltration of inflammatory cells was inhibited by an antagonist of lipoxin A4 receptor/formyl peptide receptor 2 (ALX/FPR2). The administration of 17(R)‐RvD1 at the later fibrotic stage also improved the lung failure. These results suggest that 17(R)‐RvD1 attenuates pulmonary fibrosis by promoting the resolution of neutrophilic inflammation and also provides pulmonary restoration. These data highlight the therapeutic potential of 17(R)‐RvD1 in the management of this intractable disease.

Attenuation of lung inflammation and fibrosis in CD69-deficient mice after intratracheal bleomycin

Background

Cluster of differentiation 69 (CD69), an early activation marker antigen on T and B cells, is also expressed on activated macrophages and neutrophils, suggesting that CD69 may play a role in inflammatory diseases. To determine the effect of CD69 deficiency on bleomycin(BLM)-induced lung injury, we evaluated the inflammatory response following intratracheal BLM administration and the subsequent fibrotic changes in wild type (WT) and CD69-deficient (CD69^-/-) mice.

Methods

The mice received a single dose of 3 mg/kg body weight of BLM and were sacrificed at 7 or 14 days post-instillation (dpi). Lung inflammation in the acute phase (7 dpi) was investigated by differential cell counts and cytokine array analyses of bronchoalveolar lavage fluid. In addition, lung fibrotic changes were evaluated at 14 dpi by histopathology and collagen assays. We also used reverse transcription polymerase chain reaction to measure the mRNA expression level of transforming growth factor β1 (TGF-β1) in the lungs of BLM-treated mice.

Results

CD69^-/- mice exhibited less lung damage than WT mice, as shown by reductions in the following indices: (1) loss of body weight, (2) wet/dry ratio of lung, (3) cytokine levels in BALF, (4) histological evidence of lung injury, (5) lung collagen deposition, and (6) TGF-β1 mRNA expression in the lung.

Conclusion

The present study clearly demonstrates that CD69 plays an important role in the progression of lung injury induced by BLM.

A further investigation concerning correlation between anti-fibrotic effect of liposomal quercetin and inflammatory cytokines in pulmonary fibrosis

It is widely accepted that inflammatory cells and cytokines play vital roles in the process of pulmonary fibrosis. The aim of this study was to evaluate the preventative effects of liposomal quercetin against bleomycin-induced pulmonary fibrosis in vivo. The underlying molecular mechanisms were also investigated. Bleomycin was injected intratracheally at a single dose of 5 U/kg for pulmonary fibrosis induction. Liposomal quercetin was intravenously injected 1 day prior to bleomycin administration and continued to the end of the study (for 4 weeks). Our results showed that liposomal quercetin diminished the increase of total cell counts and macrophage counts in bronchoalveolar lavage fluid. The neutrophil and lymphocyte counts were also significantly decreased both on day 7 and 14 after liposomal quercetin injection (P<0.05). The levels of TNF-alpha, IL-1beta, and IL-6 in bronchoalveolar lavage fluid at day 7 were strikingly reduced in liposomal quercetin treated group compared with bleomycin-induced group (TNF-alpha: 56.21+/-3.16 pg/ml vs.79.85+/-6.91 pg/ml; IL-1beta: 37.64+/-2.10 pg/ml vs. 73.29+/-5.78 pg/ml; IL-6: 88.52+/-5.96 pg/ml vs. 128.56+/-8.72 pg/ml; P<0.05). Moreover, the treatment with liposomal quercetin exerted approximately 35.8% reduction of the hydroxyproline content in contrast to the bleomycin-induced group (P<0.05). Histopathological assessment revealed that treatment with liposomal quercetin apparently lessened the lung fibrosis areas and collagen deposition accompanied with decreased expression of TGF-beta1. Thus, our results suggested that liposomal quercetin could attenuate the bleomycin-induced pulmonary fibrosis in vivo by the suppression of inflammatory cytokines.

Inhibition of transforming growth factor-beta signalling attenuates interleukin (IL)-18 plus IL-2-induced interstitial lung disease in mice

Interstitial lung disease (ILD) is an intractable disease induced by various factors in humans. However, there is no universally effective treatment for ILD. In this study, we investigated the role of transforming growth factor (TGF)-beta signalling in the pathogenesis of ILD by using model mice. Injection of interleukin (IL)-18 plus IL-2 in C57BL6 (B6) mice resulted in acute ILD by infiltration of natural killer (NK) cells and a significant increase of TGF-beta mRNA in the lung. To examine the pathogenetic role of TGF-beta in ILD mice, we used SB-431542 (4-[4-(1,3-benzodioxol-5-yl)-5-(2-pyridinyl)-1H-imidazol-2-yl]-benzamide), which is a potent and selective inhibitor of TGF-beta receptor I (TbetaRI), also known as activin receptor-like kinase 5 (ALK5). Treatment of B6-ILD mice with SB-431542 resulted in improvement of ILD, delay in mortality, reduction of the expression of interferon (IFN)-gamma and IL-6 in the lungs. The same treatment also decreased significantly the percentage of natural killer (NK) cells in the lungs (P < 0.05) and mRNA expression levels of certain chemokines such as CCL2, CCL3, CCL4, CCL5 and CXCL10 in B6-ILD. These findings were confirmed by IL-18 plus IL-2 treatment of Smad3-deficient (Smad3(-/-)) mice (P < 0.05). Our results showed that inhibition of TGF-beta signalling reduced the percentage of NK cells and the expression of certain chemokines in the lungs, resulting in improvement of ILD. The findings suggest that TGF-beta signalling may play an important role in the pathogenesis of IL-18 plus IL-2-induced ILD in mice.

Therapeutic effect of lecithinized superoxide dismutase on bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is thought to involve inflammatory infiltration of leukocytes, lung injury induced by reactive oxygen species (ROS), in particular superoxide anion, and fibrosis (collagen deposition). No treatment has been shown to improve definitively the prognosis for IPF patients. Superoxide dismutase (SOD) catalyzes the dismutation of superoxide anion to hydrogen peroxide, which is subsequently detoxified by catalase. Lecithinized SOD (PC-SOD) has overcome clinical limitations of SOD, including low tissue affinity and low stability in plasma. In this study, we examined the effect of PC-SOD on bleomycin-induced pulmonary fibrosis. Severity of the bleomycin-induced fibrosis in mice was assessed by various methods, including determination of hydroxyproline levels in lung tissue. Intravenous administration of PC-SOD suppressed the bleomycin-induced increase in the number of leukocytes in bronchoalveolar lavage fluid. Bleomycin-induced collagen deposition and increased hydroxyproline levels in the lung were also suppressed in animals treated with PC-SOD, suggesting that PC-SOD suppresses bleomycin-induced pulmonary fibrosis. The dose-response profile of PC-SOD was bell-shaped, but concurrent administration of catalase restored the ameliorative effect at high doses of PC-SOD. Intratracheal administration or inhalation of PC-SOD also attenuated the bleomycin-induced inflammatory response and fibrosis. The bell-shaped dose-response profile of PC-SOD was not observed for these routes of administration. We consider that, compared with intravenous administration, inhalation of PC-SOD may be a more therapeutically beneficial route of administration due to the higher safety and quality of life of the patient treated with this drug.

Role of proinflammatory cytokines IL-18 and IL-1beta in bleomycin-induced lung injury in humans and mice

Administration of several chemotherapeutic drugs, such as bleomycin, busulfan, and gefitinib, often induces lethal lung injury. However, the precise mechanisms responsible for this drug-induced lung injury are still unclear. In the present study, we examined the role of the proinflammatory cytokines IL-18 and IL-1beta in the mechanism of bleomycin-induced lung injury. We performed immunohistochemical analysis of IL-18 and IL-18 receptor (R) alpha chain expression in the lungs of five patients with bleomycin-induced lethal lung injury. Enhanced expression of both IL-18 and IL-18Ralpha was observed in the lungs of all five patients with bleomycin-induced lung injury. To support the data obtained from patient samples, the levels of IL-1beta and IL-18 mRNA and protein, pulmonary inflammation, and lung fibrosis were examined in mouse models of bleomycin-induced lung injury. Intravenous administration of bleomycin induced the expression of IL-1beta and IL-18 in the serum and lungs of wild-type C57BL/6 mice. IL-18-producing F4/80(+) neutrophils, but not CD3(+) T cells, were greatly increased in the lungs of treated mice. Moreover, bleomycin-induced lung injury was significantly attenuated in caspase-1(-/-), IL-18(-/-), and IL-18Ralpha(-/-) mice in comparison with control mice. Thus, our results provide evidence for an important role of IL-1beta and IL-18 in chemotherapy-induced lung injury.

Pulmonary fibrosis: pathogenesis, etiology and regulation

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

Differential binding of inorganic particles to MARCO

Alveolar macrophages (AM) in the lung have been documented to play pivotal roles in inflammation and fibrosis (silicosis) following inhalation of crystalline silica (CSiO(2)). In contrast, exposure to either titanium dioxide (TiO(2)) or amorphous silica (ASiO(2)) is considered relatively benign. The scavenger receptor macrophage receptor with collagenous structure (MARCO), expressed on AM, binds and internalizes environmental particles such as silica and TiO(2). Only CSiO(2) is toxic to AM, while ASiO(2) and TiO(2) are not. We hypothesize that differences in induction of pathology between toxic CSiO(2) and nontoxic particles ASiO(2) and TiO(2) may be related to their differential binding to MARCO. In vitro studies with Chinese hamster ovary (CHO) cells transfected with human MARCO and mutants were conducted to better characterize MARCO-particulate (ASiO(2), CSiO(2), and TiO(2)) interactions. Results with MARCO-transfected CHO cells and MARCO-specific antibody demonstrated that the scavenger receptor cysteine-rich (SRCR) domain of MARCO was required for particle binding for all the tested particles. Only TiO(2) required divalent cations (viz., Ca(+2) and/or Mg(+2)) for binding to MARCO, and results from competitive binding studies supported the notion that TiO(2) and both the silica particles bound to different motifs in SRCR domain of MARCO. The results also suggest that particle shape and/or crystal structure may be the determinants linking particle binding to MARCO and cytotoxicity. Taken together, these results demonstrate that the SRCR domain of MARCO is required for particle binding and that involvement of different regions of SRCR domain may distinguish downstream events following particle binding.

Alveolar macrophages from normal subjects lack the NOS-related system y+ for arginine transport

Systems y+ and y+L represent the main routes for arginine transport in mammalian cells. While system y+ activity is needed for the stimulated NO production in rodent alveolar macrophages (AM), no information is yet available about arginine transport in human AM. We study here arginine influx and genes for arginine transporters in AM from bronchoalveolar lavage of normal subjects. These cells express the y+ -related genes SLC7A1/CAT1 and SLC7A2/CAT2B, as well as the y+L genes SLC7A7/y+LAT1 and SLC7A6/y+LAT2. However, compared with human endothelial cells, AM express much less SLC7A2 mRNA and higher levels of SLC7A7 mRNA. Granulocyte macrophage colony-stimulating factor or IFN-gamma do not change the expression of any transporter gene, while lipopolysaccharide induces SLC7A2/CAT2B. Under all the conditions tested, leucine inhibits most of the arginine transport in the presence of Na+ and N-ethylmaleimide, an inhibitor of system y+, is completely ineffective, indicating that system y+L operates most of the arginine influx. Comparable results are obtained in AM from patients with interstitial lung disease, such as Nonspecific Interstitial Pneumonia (NSIP), although these cells have a higher SLC7A1 and a lower SLC7A7 expression than AM from normal subjects. It is concluded that AM from normal subjects or patients with NSIP lack a functional transport system y+, a situation that may limit arginine availability for NO synthesis. Moreover, since mutations of SLC7A7/y+LAT1 cause Lysinuric Protein Intolerance, a disease often associated with AM impairment and alveolar proteinosis, the high SLC7A7 expression observed in human AM suggests that y+LAT1 activity is important for the function of these cells.

Localization of endothelin receptors in bleomycin-induced pulmonary fibrosis in the rat

Pulmonary fibrosis is characterized by excessive extracellular matrix deposition with concomitant loss of gas exchange units, and endothelin-1 (ET-1) has been implicated in its pathogenesis. Increased levels of ET-1 from tissues and bronchoalveolar lavage have been reported in patients with pulmonary fibrosis and in animal models after intratracheal bleomycin. We characterized the cellular distribution of alveolar ET receptors by immunohistochemistry in bleomycin-induced pulmonary fibrosis in the rat and determined the regulation by bleomycin of ET receptor mRNA expression in isolated alveolar macrophages and rat lung fibroblasts. We found significant increases in the numbers of fibroblasts and macrophages at day 7 compared to day 28 and control animals. ET(B) receptor immunoreactivity was observed on fibroblasts and invading monocytes. Isolated fibroblasts expressed both ET(A) and ET(B) receptor mRNA, and ET(A) receptor mRNA was upregulated by bleomycin. Isolated resident alveolar macrophages expressed neither ET(A) nor ET(B) receptor mRNA which were also not induced by bleomycin. We conclude that, while ET(B) receptor stimulation of fibroblasts and monocytes recruited during bleomycin-induced lung injury exerts antagonistic effects on fibroblast collagen synthesis, the observed increase in the number of fibroblasts in vivo and upregulation of fibroblast ET(A) receptor mRNA by bleomycin in vitro point to a predominance of the profibrotic effects of ET receptor engagement.

A comparison of murine and human alveolar macrophage responses to urban particulate matter

There is increasing evidence linking mortality, increased asthma morbidity, and other respiratory disorders to increases in fine airborne particulate matter (PM) concentrations. However, there are only limited data dealing with the biological mechanisms that ultimately lead to the reported health effects. Rodents are frequently used as an animal model to help elucidate the mechanisms of toxicity that may provide clues for the understanding of PM toxicity in humans; however, the relationships between murine and human PM toxicity have not been established. PM is known to target the pulmonary epithelium and resident alveolar macrophages (AM). PM can initiate cytotoxic effects on the AM including apoptosis and necrosis, depending on the particle concentration, which may be central to the pathological effects just described. This study examined AM apoptosis and necrosis initiated by PM in AM from humans and BALB/c mice in an in vitro exposure model. Freshly isolated AM from human volunteers were incubated with seven different residual fractions of PM1648 derived from organic solvent extractions, high-temperature heating and acid digestions that change the surface characteristics of the original PM. These results were compared to the analogous murine experiments. The results suggested that, at the same concentration of PM, the trend of toxicity and the posttreatment effects observed in BALB/c and human AM have a similar pattern. Altering the surface chemistry by removal of one or more PM components, such as through the various treatments conducted in this study, is sufficient to alter PM bioactivity in both human and murine AM in a similar manner. In addition, the human and murine models were compared with regard to in vitro cytotoxicity using PM(2.5) particles. The cytotoxic PM(2.5) effects were identical in both human and mouse models. Regression analysis revealed that the BALB/c mouse is a suitable model for PM cytotoxicity of AM as it is a good predictive model for the human AM responses.

Alveolar macrophages from systemic sclerosis patients: evidence for IL-4-mediated phenotype changes

The mechanism of chronic lung inflammation leading to lung fibrosis is unknown and does not have a characteristic inflammatory macrophage phenotype. This study was undertaken to determine whether a change in macrophage phenotype could account for chronic lung inflammation. In this study, human alveolar macrophages (AM) from subjects with systemic sclerosis (SSc) were obtained from bronchoalveolar lavage (BAL) and characterized on the basis of function (response to LPS), phenotype, and relative cell-surface B7 expression. AM from the subjects' disease-involved and noninvolved lung lobes were compared with each other and to AM from normal volunteer BAL. AM from involved SSc lobes produced significantly more interleukin (IL)-1β and PGE2than AM from uninvolved lobes in response to LPS, but there was no spontaneous production of either mediator. The activator AM phenotype designated by RFD1+ surface epitope was significantly elevated in SSc BAL samples compared with normal BAL, although there were no differences comparing involved vs. noninvolved lobes within SSc subjects. The major histocompatibility complex II costimulatory molecule B7.2 was also significantly elevated in SSc AM compared with normal AM, again with no differences between involved and noninvolved lobes. In an attempt to determine environmental influences on AM phenotypes, normal AM were cultured in vitro with IFN-γ, IL-3, IL-4, IL-10, IL-12, or dexamethasone for 6 days. Of the cytokines examined, only IL-4 induced significant increases in both the activator phenotype RFD1+ and B7.2 expression. Taken together, these results indicate that IL-4 could account for proinflammatory AM phenotype changes and B7 surface-marker shifts, as seen in subjects with SSc.

Human SP-A genetic variants and bleomycin-induced cytokine production by THP-1 cells: effect of ozone-induced SP-A oxidation

Surfactant protein A (SP-A) plays a role in innate host defense. Human SP-A is encoded by two functional genes (SP-A1 and SP-A2), and several alleles have been characterized for each gene. We assessed the effect of in vitro expressed human SP-A genetic variants, on TNF-alpha and IL-8 production by THP-1 cells in the presence of bleomycin, either before or after ozone-induced oxidation of the variants. The oligomerization of SP-A variants was also examined. We found 1) cytokine levels induced by SP-A2 (1A, 1A(0)) were significantly higher than those by SP-A1 (6A(2), 6A(4)) in the presence of bleomycin. 2) In the presence of bleomycin, ozone-induced oxidation significantly decreased the ability of 1A and 1A/6A(4), but not of 6A(4), to stimulate TNF-alpha production. 3) The synergistic effect of bleomycin/SP-A, either before or after oxidation, can be inhibited to the level of bleomycin alone by surfactant lipids. 4) Differences in oligomerization were also observed between SP-A1 and SP-A2. The results indicate that differences among SP-A variants may partly explain the individual variability of pulmonary complications observed during bleomycin chemotherapy and/or in an environment that may promote protein oxidation.

In vivo antioxidant treatment protects against bleomycin-induced lung damage in rats

1. This study examines the activity of the antioxidant N-acetylcysteine on bleomycin-induced pulmonary fibrosis in rats with emphasis on the early inflammatory phase. 2. Rats receiving N-acetylcysteine (300 mg kg(-1) day(-1), intraperitoneal) had less augmented lung wet weight, and lower levels of proteins, lactate dehydrogenase, neutrophil and macrophage counts in bronchoalveolar lavage fluid and lung myeloperoxidase activity with a betterment of histological score at 3 days postbleomycin. 3. A diminished lung GSH/GSSG ratio and augmented lipid hydroperoxides were observed 3 days postbleomycin. These changes were attenuated by N-acetylcysteine. Alveolar macrophages from bleomycin-exposed rats released augmented amounts of superoxide anion and nitric oxide. N-Acetylcysteine did not modify superoxide anion generation but reduced the increased production of nitric oxide. 4. N-Acetylcysteine suppressed the bleomycin-induced increased activation of lung NF-kappaB (shift assay and immunohistochemistry), and decreased the augmented levels of the early inflammatory cytokines, tumour necrosis factor-alpha, interleukin-beta, interleukin-6 and macrophage inflammatory protein-2 observed in bronchoalveolar lavage fluid at 1 and 3 days postbleomycin exposure. 5. At 15 days postbleomycin, N-acetylcysteine decreased collagen deposition in bleomycin-exposed rats (hydroxyproline content: 6351+/-669 and 4626+/-288 micro g per lung in drug vehicle- and N-acetylcysteine-treated rats, respectively; P<0.05). Semiquantitative histological assessment at this stage showed less collagen deposition in N-acetylcysteine-treated rats compared to those receiving bleomycin alone. 6. These results indicate that N-acetylcysteine reduces the primary inflammatory events, thus preventing cellular damage and the subsequent development of pulmonary fibrosis in the bleomycin rat model.

Bleomycin-induced lung fibrosis in IL-4-overexpressing and knockout mice

The role of IL-4 in the development of lung fibrosis is as yet unclear. Bleomycin (Bleo) or saline (Sal) was injected intratracheally into three groups of C57BL/6J mice: transgenic animals that overexpressed IL-4 (IL-4 TG, n = 14), mice with a targeted knockout mutation of the IL-4 gene (IL-4 KO, n = 11), and wild-type (WT, n = 13) mice. At 14 days, lung fibrosis was evaluated by hydroxyproline measurement and by quantitative image analysis of fibrosis fraction and alveolar wall area fraction. Bronchoalveolar lavage cell counts in all Bleo-treated groups demonstrated an increased percentage of lymphocytes with a corresponding decrease in the percentage of macrophages. Comparing Bleo- to Sal-treated controls within each group of mice showed increases in all lung fibrosis parameters in IL-4 KO and WT, but not in any of the parameters in IL-4 TG mice. The severity of Bleo-induced fibrotic response was decreased in overexpressed IL-4 TG compared with IL-4 KO mice. These data negate a critical profibrotic role for IL-4 in Bleo-induced lung fibrosis.

Combined SP-A-bleomycin effect on cytokines by THP-1 cells: impact of surfactant lipids on this effect

Surfactant protein A (SP-A) plays a role in host defense and inflammation in the lung. In the present study, we investigated the hypothesis that SP-A is involved in bleomycin-induced pulmonary fibrosis. We studied the effects of human SP-A on bleomycin-induced cytokine production and mRNA expression in THP-1 macrophage-like cells and obtained the following results. 1) Bleomycin-treated THP-1 cells increased tumor necrosis factor (TNF)-alpha, interleukin (IL)-8, and IL-1beta production in dose- and time-dependent patterns, as we have observed with SP-A. TNF-alpha levels were unaffected by treatment with cytosine arabinoside. 2) The combined bleomycin-SP-A effect on cytokine production is additive by RNase protection assay and synergistic by enzyme-linked immunosorbent assay. 3) Although the bleomycin effect on cytokine production was not significantly affected by the presence of surfactant lipid, the additive and synergistic effect of SP-A-bleomycin on cytokine production was significantly reduced. We speculate that the elevated cytokine levels resulting from the bleomycin-SP-A synergism are responsible for bleomycin-induced pulmonary fibrosis and that surfactant lipids can help ameliorate pulmonary complications observed during bleomycin chemotherapy.

Expression of TNF and the necessity of TNF receptors in bleomycin-induced lung injury in mice

Bleomycin (BLM) induction of lung fibrosis in mice is an established model to study the mechanism of pulmonary fibrosis. Cytokine secretion has been implicated as a fundamental component of the lung fibrotic process observed in response to BLM. Among the cytokines implicated in lung fibrosis, Tumor necrosis factor (TNF) alpha has been considered to play a fundamental role. In the present study, we characterized the cellular sources of TNF during BLM-induced lung injury and examined the importance of TNF receptors in this process. To characterize the expression of TNF, we utilized two strains of mice, one sensitive (C57BL/6) and one resistant (BALB/c) to BLM-induced lung injury. Mice received BLM (120 mg/kg total) or saline, as control, by multiple subcutaneous injections. BLM induced the development of inflammation in subpleural areas only in the lungs of BLM-sensitive mice. These subpleural areas were characterized by infiltration of CD68-positive macrophages and increased collagen deposition. BLM enhanced the expression of TNF mRNA in BLM-sensitive, but not in BLM-resistant, mice. In situ hybridization studies localized the expression of TNF in the areas of BLM-induced inflammation in 6% and 27% of macrophages at 14 and 21 days post BLM treatment. In addition to TNF, BLM exposure resulted in the upregulated expression of transforming growth factor (TGF)-beta 1, but not interleukin (IL)-1, mRNA in the lungs of both murine strains at 14 and 21 days. This upregulated expression of TGF-beta 1 mRNA was greater in the lungs of BLM-sensitive mice. In separate experiments, double TNF receptor knockout mice were exposed to BLM. These animals demonstrated an increased expression of TNF, but not TGF-beta 1, mRNA in response to BLM and did not exhibit histologic evidence of lung injury following BLM exposure. In summary, the upregulation of TNF mRNA in macrophages correlated with the appearance of inflammation following BLM exposure and was limited to the BLM-sensitive strain. Furthermore, in addition to the release of the TNF ligand, it appears that the presence of TNF receptors is necessary for the development of BLM-induced lung injury, and signaling through these receptors may contribute to the regulation of the TGF-beta 1 mRNA expression observed in response to bleomycin. These results provide further support for a role of macrophages and TNF in the induction of lung inflammation.

Human alveolar macrophage cytokine release in response to in vitro and in vivo asbestos exposure

The lung macrophage is proposed to be involved in the development of asbestos-induced pulmonary fibrosis. Knowledge of the effects of long-term asbestos exposure on lung macrophage cytokine release should better define the role of the macrophage in fibrogenesis. This study examines the effects of acute in vitro asbestos exposure and chronic in vivo asbestos exposure on human alveolar macrophage cytokine release. As indicators of asbestos-induced macrophage activation, the cellular release of IL-1 beta, TNF-alpha, IL-6, GM-CSF, and PGE2 was measured during a 24-h in vitro culture. Alveolar macrophages from normal volunteers were cultured in vitro with chrysotile asbestos. Of the factors measured, only TNF-alpha was elevated in response to asbestos exposure. Alveolar macrophages from asbestos-exposed individuals were placed into one of two groups based on their exposure history. These two groups were matched for age, smoking history, and diagnosis; none met the criteria for asbestosis. Cells isolated from subjects that had been exposed to asbestos for more than 10 years secreted enhanced basal amounts of IL-1 beta, TNF-alpha, IL-6, and PGE2, while those who had been exposed for less than 10 years did not. The results indicate that while asbestos had minimal acute effects on cytokine production by the human alveolar macrophage, intense, chronic exposure to asbestos leads to the enhanced basal release of significant amounts of several cytokines that have activity for the fibroblast, even in the absence of overt fibrosis.