Systemic inhibition of NF-kappaB activation protects from silicosis

Inflammation pathways as therapeutic targets in angiotensin II induced atrial fibrillation

Atrial fibrillation (AF), a common cardiac arrhythmia, is associated with severe complications such as stroke and heart failure. Although the precise mechanisms underlying AF remain elusive, inflammation is acknowledged as a pivotal factor in its progression. Angiotensin II (AngII) is implicated in promoting atrial remodeling and inflammation. However, the exact pathways through which AngII exacerbates AF are still not fully defined. This study explores the key molecular mechanisms involved, including dysregulation of calcium ions, altered connexin expression, and activation of signaling pathways such as TGF-β, PI3K/AKT, MAPK, NF-κB/NLRP3, and Rac1/JAK/STAT3. These pathways are instrumental in contributing to atrial fibrosis, electrical remodeling, and increased susceptibility to AF. Ang II-induced inflammation disrupts ion channel function, resulting in structural and electrical remodeling of the atria and significantly elevating the risk of AF. Anti-inflammatory treatments such as RAAS inhibitors, colchicine, and statins have demonstrated potential in reducing the incidence of AF, although clinical outcomes are inconsistent. This manuscript underscores the link between AngII-induced inflammation and the development of AF, proposing the importance of targeting inflammation in the management of AF.

A comprehensive retrospect on the current perspectives and future prospects of pneumoconiosis

Pneumoconiosis is a widespread occupational pulmonary disease caused by inhalation and retention of dust particles in the lungs, is characterized by chronic pulmonary inflammation and progressive fibrosis, potentially leading to respiratory and/or heart failure. Workers exposed to dust, such as coal miners, foundry workers, and construction workers, are at risk of pneumoconiosis. This review synthesizes the international and national classifications, epidemiological characteristics, strategies for prevention, clinical manifestations, diagnosis, pathogenesis, and treatment of pneumoconiosis. Current research on the pathogenesis of pneumoconiosis focuses on the influence of autophagy, apoptosis, and pyroptosis on the progression of the disease. In addition, factors such as lipopolysaccharide and nicotine have been found to play crucial roles in the development of pneumoconiosis. This review provides a comprehensive summary of the most fundamental achievements in the treatment of pneumoconiosis with the purpose of indicating the future direction of its treatment and control. New technologies of integrative omics, artificial intelligence, systemic administration of mesenchymal stromal cells have proved useful in solving the conundrum of pneumoconiosis. These directional studies will provide novel therapeutic targets for the treatment of pneumoconiosis.

The role of inflammation in silicosis

Silicosis is a chronic illness marked by diffuse fibrosis in lung tissue resulting from continuous exposure to SiO2-rich dust in the workplace. The onset and progression of silicosis is a complicated and poorly understood pathological process involving numerous cells and molecules. However, silicosis poses a severe threat to public health in developing countries, where it is the most prevalent occupational disease. There is convincing evidence supporting that innate and adaptive immune cells, as well as their cytokines, play a significant role in the development of silicosis. In this review, we describe the roles of immune cells and cytokines in silicosis, and summarize current knowledge on several important inflammatory signaling pathways associated with the disease, aiming to provide novel targets and strategies for the treatment of silicosis-related inflammation.

Inhibition of antiapoptotic BCL-2 proteins with ABT-263 induces fibroblast apoptosis, reversing persistent pulmonary fibrosis

Patients with progressive fibrosing interstitial lung diseases (PF-ILDs) carry a poor prognosis and have limited therapeutic options. A hallmark feature is fibroblast resistance to apoptosis, leading to their persistence, accumulation, and excessive deposition of extracellular matrix. A complex balance of the B cell lymphoma 2 (BCL-2) protein family controlling the intrinsic pathway of apoptosis and fibroblast reliance on antiapoptotic proteins has been hypothesized to contribute to this resistant phenotype. Examination of lung tissue from patients with PF-ILD (idiopathic pulmonary fibrosis and silicosis) and mice with PF-ILD (repetitive bleomycin and silicosis) showed increased expression of antiapoptotic BCL-2 family members in α-smooth muscle actin-positive fibroblasts, suggesting that fibroblasts from fibrotic lungs may exhibit increased susceptibility to inhibition of antiapoptotic BCL-2 family members BCL-2, BCL-XL, and BCL-W with the BH3 mimetic ABT-263. We used 2 murine models of PF-ILD to test the efficacy of ABT-263 in reversing established persistent pulmonary fibrosis. Treatment with ABT-263 induced fibroblast apoptosis, decreased fibroblast numbers, and reduced lung collagen levels, radiographic disease, and histologically evident fibrosis. Our studies provide insight into how fibroblasts gain resistance to apoptosis and become sensitive to the therapeutic inhibition of antiapoptotic proteins. By targeting profibrotic fibroblasts, ABT-263 offers a promising therapeutic option for PF-ILDs.

Preclinical Mouse Model of Silicosis

Silicosis is an untreatable occupational lung disease caused by chronic inhalation of crystalline silica. Cyclical release and reuptake of silica particles by macrophages and airway epithelial cells causes repeated tissue damage, characterized by widespread inflammation and progressive diffuse fibrosis. While inhalation is the main route of entry for silica particles in humans, most preclinical studies administer silica via the intratracheal route. In vivo mouse models of lung disease are valuable tools required to bridge the translational gap between in vitro cell culture and human disease. This chapter describes a mouse model of silicosis which mimics clinical features of human silicosis, as well as methods for intranasal instillation of silica and disease analysis. Lung tissue can be collected for histological assessment of silica particle distribution, inflammation, structural damage, and fibrosis in sections stained with hematoxylin and eosin or Masson's trichrome. This approach can be extended to other chronic fibrotic lung diseases where inhalation of small damaging particles such as pollutants causes irreversible disease.

Role of metabolic reprogramming in pro-inflammatory cytokine secretion from LPS or silica-activated macrophages

In the lungs, macrophages constitute the first line of defense against pathogens and foreign bodies and play a fundamental role in maintaining tissue homeostasis. Activated macrophages show altered immunometabolism and metabolic changes governing immune effector mechanisms, such as cytokine secretion characterizing their classic (M1) or alternative (M2) activation. Lipopolysaccharide (LPS)-stimulated macrophages demonstrate enhanced glycolysis, blocked succinate dehydrogenase (SDH), and increased secretion of interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α). Glycolysis suppression using 2 deoxyglucose in LPS-stimulated macrophages inhibits IL-1β secretion, but not TNF-α, indicating metabolic pathway specificity that determines cytokine production. In contrast to LPS, the nature of the immunometabolic responses induced by non-organic particles, such as silica, in macrophages, its contribution to cytokine specification, and disease pathogenesis are not well understood. Silica-stimulated macrophages activate pattern recognition receptors (PRRs) and NLRP3 inflammasome and release IL-1β, TNF-α, and interferons, which are the key mediators of silicosis pathogenesis. In contrast to bacteria, silica particles cannot be degraded, and the persistent macrophage activation results in an increased NADPH oxidase (Phox) activation and mitochondrial reactive oxygen species (ROS) production, ultimately leading to macrophage death and release of silica particles that perpetuate inflammation. In this manuscript, we reviewed the effects of silica on macrophage mitochondrial respiration and central carbon metabolism determining cytokine specification responsible for the sustained inflammatory responses in the lungs.

Gefitinib and fostamatinib target EGFR and SYK to attenuate silicosis: a multi-omics study with drug exploration

Silicosis is the most prevalent and fatal occupational disease with no effective therapeutics, and currently used drugs cannot reverse the disease progress. Worse still, there are still challenges to be addressed to fully decipher the intricated pathogenesis. Thus, specifying the essential mechanisms and targets in silicosis progression then exploring anti-silicosis pharmacuticals are desperately needed. In this work, multi-omics atlas was constructed to depict the pivotal abnormalities of silicosis and develop targeted agents. By utilizing an unbiased and time-resolved analysis of the transcriptome, proteome and phosphoproteome of a silicosis mouse model, we have verified the significant differences in transcript, protein, kinase activity and signaling pathway level during silicosis progression, in which the importance of essential biological processes such as macrophage activation, chemotaxis, immune cell recruitment and chronic inflammation were emphasized. Notably, the phosphorylation of EGFR (p-EGFR) and SYK (p-SYK) were identified as potential therapeutic targets in the progression of silicosis. To inhibit and validate these targets, we tested fostamatinib (targeting SYK) and Gefitinib (targeting EGFR), and both drugs effectively ameliorated pulmonary dysfunction and inhibited the progression of inflammation and fibrosis. Overall, our drug discovery with multi-omics approach provides novel and viable therapeutic strategies for the treatment of silicosis.

A Novel N-Arylpyridone Compound Alleviates the Inflammatory and Fibrotic Reaction of Silicosis by Inhibiting the ASK1-p38 Pathway and Regulating Macrophage Polarization

Silicosis is one of the potentially fatal occupational diseases characterized by respiratory dysfunction, chronic interstitial inflammation, and fibrosis, for which treatment options are limited. Previous studies showed that a novel N-arylpyridone compound named AKEX0011 exhibited anti-inflammatory and anti-fibrotic effects in bleomycin-induced pulmonary fibrosis; however, it is unknown whether it could also be effective against silicosis. Therefore, we sought to investigate the preventive and therapeutic roles of AKEX0011 in a silicosis rodent model and in a silica-stimulated macrophage cell line. In vivo, our results showed that AKEX0011 ameliorated silica-induced imaging lung damages, respiratory dysfunction, reduced the secretion of inflammatory and fibrotic factors (TNF-α, IL-1β, IL-6, TGF-β, IL-4, and IL-10), and the deposition of fibrosis-related proteins (collagen I, fibronectin, and α-SMA), regardless of early or advanced therapy. Specifically, we found that AKEX0011 attenuated silicosis by inhibiting apoptosis, blocking the ASK1-p38 MAPK signaling pathway, and regulating polarization of macrophages. In vitro, AKEX0011 inhibited macrophages from secreting inflammatory cytokines and inhibited apoptosis of macrophages in pre-treated and post-treated models, concurrent with blocking the ASK1-p38 pathway and inhibiting M1 polarization. Collectively, AKEX0011, as a novel N-arylpyridone compound, exerted protective effects for silica-induced pulmonary inflammation and fibrosis both in vivo and in vitro, and hence, it could be a strong drug candidate for the treatment of silicosis.

Another One Fights the Dust - Targeting the NLRP3 Inflammasome for the Treatment of Silicosis

Silicosis is a multifaceted lung disease, characterised by persistent inflammation and structural remodelling. Despite its poor prognosis, there are no treatments currently available for patients with silicosis. Recent pre-clinical findings in models of lung fibrosis have suggested a major role for the nucleotide binding domain and leucine-rich repeat pyrin domain containing 3 (NLRP3) inflammasome in silica-driven inflammation and fibrosis. This review outlines the beneficial effects of targeting the NLRP3 inflammasome in in vitro cell experiments and in in vivo animal models, whereby inflammation and fibrosis are abrogated following NLRP3 inflammasome inhibition. While preclinical evidence is promising, studies which explore NLRP3 inflammasomes in the clinical setting are warranted. In particular, there is still a need to identify biomarkers which may be helpful for the early detection of silicosis and to fully elucidate mechanisms underlying these beneficial effects to further develop or repurpose existing anti-NLRP3 drugs as novel treatments that limit disease progression.

Necroptosis in pulmonary macrophages promotes silica-induced inflammation and interstitial fibrosis in mice

Silicosis is a disease characterized by extensive lung nodules and fibrosis caused by the prolonged inhalation of silica in occupational settings. However, the molecular mechanism of silicosis development is complex and not fully understood. Furthermore, the role of necroptosis, a death receptor-mediated and caspase-independent mode of inflammatory cell death, is not well understood in silicosis. Here, we demonstrate that the necroptotic signaling pathway of macrophages is significantly activated in the lungs of silicosis mouse models. Meanwhile, increased M1 macrophage infiltration and up-regulation of pro-inflammatory cytokines (TNF-α, IL-6) were observed in our silicosis model. Notably, the expression of the pro-fibrotic factor, TGF-β1, and fibrosis biomarkers α-SMA and collagen I were also unregulated; however, these phenomena were recovered by Nec-1, an inhibitor specific for RIP1 kinase-dependent necroptosis. We conclude that macrophage-mediated necroptosis promotes the progression of silicosis by enhancing lung inflammatory responses and fibrogenesis in a mouse model of silicosis. These findings provide new insights for drug discovery and clinical treatment of silicosis.

Caveolin-1 negatively regulates inflammation and fibrosis in silicosis

Inhalation of crystalline silica causes silicosis, the most common and serious occupational disease, which is characterized by progressive lung inflammation and fibrosis. Recent studies revealed the anti-inflammatory and anti-fibrosis role of Caveolin-1 (Cav-1) in lung, but this role in silicosis has not been investigated. Thus, this study evaluated Cav-1 regulatory effects in silicosis. It was found that Cav-1 levels were significantly reduced in the lung from silicosis patients and silicotic mice. The silicosis models were established in C57BL/6 (wild-type) and Cav-1 deficiency (Cav-1^-/- ) mice, and Cav-1^-/- mice displayed wider alveolar septa, increased collagen deposition and more silicotic nodules. The mice peritoneal-derived macrophages were used to explore the role of Cav-1 in silica-induced inflammation, which plays a central role in mechanism of silicosis. Cav-1 inhibited silica-induced infiltration of inflammatory cells and secretion of inflammatory factors in vitro and in vivo, partly by downregulating NF-κB pathway. Additionally, silica uptake and expression of 4-hydroxynonenal in silicotic mice were observed, and it was found that Cav-1 absence triggered excessive silica deposition, causing a stronger oxidative stress response. These findings demonstrate the protective effects of Cav-1 in silica-induced lung injury, suggesting its potential therapeutic value in silicosis.

Metabolic Adaptation of Macrophages as Mechanism of Defense against Crystalline Silica

Silicosis is a lethal pneumoconiosis for which no therapy is available. Silicosis is a global threat, and more than 2.2 million people per year are exposed to silica in the United States. The initial response to silica is mediated by innate immunity. Phagocytosis of silica particles by macrophages is followed by recruitment of mitochondria to phagosomes, generation of mitochondrial reactive oxygen species, and cytokine (IL-1β, TNF-α, IFN-β) release. In contrast with LPS, the metabolic remodeling of silica-exposed macrophages is unclear. This study contrasts mitochondrial and metabolic alterations induced by LPS and silica on macrophages and correlates them with macrophage viability and cytokine production, which are central to the pathogenesis of silicosis. Using high-resolution respirometer and liquid chromatography-high-resolution mass spectrometry, we determined the effects of silica and LPS on mitochondrial respiration and determined changes in central carbon metabolism of murine macrophage cell lines RAW 264.7 and IC-21. We show that silica induces metabolic reprogramming of macrophages. Silica, as well as LPS, enhances glucose uptake and increases aerobic glycolysis in macrophages. In contrast with LPS, silica affects mitochondria respiration, reducing complex I and enhancing complex II activity, to sustain cell viability. These mitochondrial alterations are associated in silica, but not in LPS-exposed macrophages, with reductions of tricarboxylic acid cycle intermediates, including succinate, itaconate, glutamate, and glutamine. Furthermore, in contrast with LPS, these silica-induced metabolic adaptations do not correlate with IL-1β or TNF-α production, but with the suppressed release of IFN-β. Our data highlight the importance of complex II activity and tricarboxylic acid cycle remodeling to macrophage survival and cytokine-mediated inflammation in silicosis.

The interplay of DAMPs, TLR4, and proinflammatory cytokines in pulmonary fibrosis

Pulmonary fibrosis is a chronic debilitating condition characterized by progressive deposition of connective tissue, leading to a steady restriction of lung elasticity, a decline in lung function, and a median survival of 4.5 years. The leading causes of pulmonary fibrosis are inhalation of foreign particles (such as silicosis and pneumoconiosis), infections (such as post COVID-19), autoimmune diseases (such as systemic autoimmune diseases of the connective tissue), and idiopathic pulmonary fibrosis. The therapeutics currently available for pulmonary fibrosis only modestly slow the progression of the disease. This review is centered on the interplay of damage-associated molecular pattern (DAMP) molecules, Toll-like receptor 4 (TLR4), and inflammatory cytokines (such as TNF-α, IL-1β, and IL-17) as they contribute to the pathogenesis of pulmonary fibrosis, and the possible avenues to develop effective therapeutics that disrupt this interplay.

Inhibition of NF-κB by ACT001 reduces fibroblast activity in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease of unknown etiology and poor prognosis. In IPF, aberrant extracellular matrix production by activated, hyperproliferative fibroblasts drives disease progression but the exact mechanisms by which this occurs remains undefined. The transcription factor nuclear factor kappa-B (NF-ĸB) has been suggested as a potential therapeutic target in IPF and therefore the aim of this study was to investigate the efficacy of ACT001, an NF-ĸB inhibitor, on primary fibroblasts derived from patients with and without IPF. Primary lung fibroblasts derived from eight patients with IPF and eight age-matched non-diseased controls (NDC) were treated with 0-10 µM ACT001 and the effects on fibroblast activity (viability and proliferation, fibroblast-to-myofibroblast transition, fibronectin expression), interleukin (IL)-6 and IL-8 cytokine release were quantified. ACT001 inhibited fibroblast activity in a concentration-dependent manner in both groups of fibroblasts. ACT001 inhibited IL-6 but not IL-8 production in unstimulated fibroblasts. ACT001 is a water-soluble compound with a stable half-life in plasma, thus making it an attractive candidate for further investigation as a therapeutic in IPF. This study adds to the growing body of literature that demonstrates anti-fibrotic activity of NF-ĸB inhibition in the context of IPF.

Emodin attenuates silica-induced lung injury by inhibition of inflammation, apoptosis and epithelial-mesenchymal transition

Silicosis is a fatal pulmonary disease caused by the inhalation of silica dust, and characterized by inflammation and fibrosis of the lung, with no effective treatment to date. Here we investigate the effect of emodin, an anthraquinone derivative isolated from rhubarb using a mouse silicosis model and in vitro cultured human macrophages and alveolar epithelial cells. Results from histological examination indicated that emodin reduced the degree of alveolitis and fibrosis in the lungs of mice exposed to silica particles. We also demonstrated that emodin effectively inhibited the phosphorylation of Smad3 and NF-κB and reduced the levels of inflammatory factors in the lung tissue of mice treated with silica particles. In addition, we found that emodin inhibited apoptosis and demonstrated an anti-fibrotic effect by down-regulating the pro-apoptotic protein Bax and up-regulating the anti-apoptotic protein Bcl-2. Furthermore, emodin increased E-cadherin levels, reduced the expression of Vimentin, α-SMA and Col-I, as well as pro-inflammatory factors TGF-β1, TNF-α and IL-1β in vivo and in vitro. These results suggested that emodin can regulate epithelial-mesenchymal transition (EMT) through the inhibition of the TGF-β1/Smad3 signaling pathway and the NF-κB signaling pathway to prevent alveolar inflammation and apoptotic process. Overall, this study showed that emodin can alleviate pulmonary fibrosis in silicosis through regulating the inflammatory response and fibrotic process at multiple levels.

Is individual genetic susceptibility a link between silica exposure and development or severity of silicosis? A systematic review

BACKGROUND

Silicosis is a lung disease of fibrotic nature resulting from the inhalation and deposition of dust containing crystalline silica. Subjects exposed to the same environmental factors may show distinct radiological manifestations, and since silicosis is known as a multifactorial disease, it is plausible that individual genetic susceptibility may play a role in the pathology. This review of the literature aims to provide an assessment of the present data on the genetic association studies in silicosis and describe the genes that potentially might influence silicosis susceptibility in silica-exposed individuals.

METHODS

We accessed the database of PubMed for articles published in English about interindividual genetic susceptibility to silicosis using terms related to the subject matter.

RESULTS

Following the evaluation process, 28 studies were included in this systematic review, including 23 original studies and 5 meta-analyses.

CONCLUSIONS

Regardless of the advances in the knowledge of the importance of gene variations in silicosis, more studies need to be performed, in particular, special polygenic and genome-wide investigations.

miR-135a Alleviates Silica-Induced Pulmonary Fibrosis by Targeting NF-κB/Inflammatory Signaling Pathway

Silica exposure triggers inflammatory response and pulmonary fibrosis that is a severe occupational or environmental lung disease with no effective therapies. The complicated biological and molecular mechanisms underlying silica-induced lung damages have not yet been fully understood. miR-135a inhibits inflammation, apoptosis, and cancer cell proliferation. But the roles of miRNA135a involved in the silica-induced lung damages remain largely unexplored. We investigated the roles and mechanisms of miR-135a underlying silica-induced pulmonary fibrosis. The present study showed silica exposure caused the decrease in miR-135a level but the increase in inflammatory mediators. Transduction of lentivirus expressing miR-135a reduced the level of inflammatory mediators in lung tissues from silica-treated mice and improved pulmonary fibrosis which was consistent with the downregulated α-SMA but enhanced E-cadherin. Moreover, miR-135a overexpression inhibited p-p65 level in lung tissues. Overexpression of miR-135a inhibitor strengthened TLR4 protein level and NF-κB activation in BEAS-2B cells. Injection of PDTC, an inhibitor of NF-κB, further reinforced miR-135a-mediated amelioration of inflammation and pulmonary fibrosis induced by silica. The collective data indicate miR-135a restrains NF-κB activation probably through targeting TLR4 to alleviate silica-induced inflammatory response and pulmonary fibrosis.

Microenvironmental Alterations in Carbon Nanotube-Induced Lung Inflammation and Fibrosis

Carbon nanotube (CNT)-induced pulmonary inflammation and fibrosis have been intensively observed and characterized in numerous animal studies in the past decade. Remarkably, CNT-induced fibrotic lesions highly resemble some human fibrotic lung diseases, such as IPF and pneumoconiosis, regarding disease development and pathological features. This notion leads to a serious concern over the health impact of CNTs in exposed human populations, considering the rapidly expanding production of CNT materials for diverse industrial and commercial applications, and meanwhile provides the rationale for exploring CNT-induced pathologic effects in the lung. Accumulating mechanistic understanding of CNT lung pathology at the systemic, cellular, and molecular levels has demonstrated the potential of using CNT-exposed animals as a new disease model for the studies on inflammation, fibrosis, and the interactions between these two disease states. Tissue microenvironment plays critical roles in maintaining homeostasis and physiological functions of organ systems. When aberrant microenvironment forms under intrinsic or extrinsic stimulation, tissue abnormality, organ dysfunction, and pathological outcomes are induced, resulting in disease development. In this article, the cellular and molecular alterations that are induced in tissue microenvironment and implicated in the initiation and progression of inflammation and fibrosis in CNT-exposed lungs, including effector cells, soluble mediators, and functional events exemplified by cell differentiation and extracellular matrix (ECM) modification, are summarized and discussed. This analysis would provide new insights into the mechanistic understanding of lung inflammation and fibrosis induced by CNTs, as well as the development of CNT-exposed animals as a new model for human lung diseases.

In Vivo Activation and Pro-Fibrotic Function of NF-κB in Fibroblastic Cells During Pulmonary Inflammation and Fibrosis Induced by Carbon Nanotubes

Exposure to insoluble particles in the lung elicits inflammatory responses that eliminate deposited particulates and repair damaged tissue. Overzealous or prolonged responses lead to chronic conditions, such as fibrosis and malignancy, which are frequently progressive and refractory to drug therapy leading to high rates of disability and mortality. The molecular events underlying the progression of lung inflammation to chronic pathology, in particular, the conversion to fibrosis, remain poorly understood. Fibrogenic multi-walled carbon nanotubes (MWCNTs) have been shown to stimulate prominent acute inflammation that evolves into chronic lesions characterized by chronic inflammation, interstitial fibrosis, and granulomas in mouse lungs. In this communication, we examined the in vivo activation of nuclear factor-κB (NF-κB) signaling in fibroblastic cells during the inflammatory and fibrotic progression induced by MWCNTs. Wild-type C57BL/6J male mice were exposed to two fibrogenic MWCNTs (Mitsui XNRI MWNT-7 and long MWCNTs) by pharyngeal aspiration. Both MWCNTs strongly stimulated the nuclear translocation of NF-κB p65 in lung fibroblasts and myofibroblasts during the acute and chronic responses. Phosphorylated NF-κB p65 at serine 276, a marker of NF-κB activation, was markedly induced by MWCNTs in the nucleus of fibroblastic cells. Moreover, two NF-κB-regulated genes encoding pro-fibrotic mediators, tissue inhibitor of metalloproteinase 1 (TIMP1), and osteopontin (OPN), respectively, were significantly induced in lung fibroblasts and myofibroblasts. These results demonstrate that NF-κB is activated to mediate transactivation of pro-fibrotic genes in fibroblastic cells during pulmonary acute and chronic responses to CNTs, providing a mechanistic framework for analyzing gene regulation in pulmonary fibrotic progression through NF-κB signaling.

Downregulation of calponin 2 contributes to the quiescence of lung macrophages

Calponin 2 is an actin cytoskeleton-associated regulatory protein that inhibits the activity of myosin-ATPase and cytoskeleton dynamics. Recent studies have demonstrated that deletion of calponin 2 restricts the proinflammatory activation of macrophages in atherosclerosis and arthritis to attenuate the disease progression in mice. Here we demonstrate that the levels of calponin 2 vary among different macrophage populations, which may reflect their adaptation to specific tissue microenvironment corresponding to specific functional states. Interestingly, lung resident macrophages express significantly lower calponin 2 than peritoneal resident macrophages, which correlates with decreased substrate adhesion and reduced expression of proinflammatory cytokines and a proresolution phenotype. Deletion of calponin 2 in peritoneal macrophages also decreased substrate adhesion and downregulated the expression of proinflammatory cytokines. Providing the first line of defense against microbial invasion while receiving constant exposure to extrinsic antigens, lung macrophages need to maintain a necessary level of activity while limiting exaggerated inflammatory reaction. Therefore, their low level of calponin 2 may reflect an important physiological adaption. Downregulation of calponin 2 in macrophages may be targeted as a cytoskeleton-based novel mechanism, possibly via endoplasmic reticulum stress altering the processing and secretion of cytokines, to regulate immune response and promote quiescence for the treatment of inflammatory diseases.

Artificial Stone Associated Silicosis: A Systematic Review

Silicosis is a progressive fibrotic lung disease that is caused by the inhalation of respirable crystalline silica. Due to its high silica content, artificial stone (AS) can become a possible source of hazardous dust exposure for workers that are employed in the manufacturing, finishing, and installing of AS countertops. Therefore, the aim of this review was to verify the association between AS derived silica exposure and silicosis development, and also then define the pathological characteristics of the disease in relation to specific work practices and preventive and protective measures that were adopted in the workplace. A systematic review of articles available on Pubmed, Scopus, and Isi Web of Knowledge databases was performed. Although the characteristics of AS-associated silicosis were comparable to those that were reported for the disease in traditional silica exposure settings, some critical issues emerged concerning the general lack of suitable strategies for assessing/managing silica risks in these innovative occupational fields. Further research that is designed to assess the hazardous properties of AS dusts, levels of exposure in workplaces, and the effectiveness of protective equipment appears to be needed to increase awareness concerning AS risks and induce employers, employees, and all factory figures that are engaged in prevention to take action to define/adopt proper measures to protect the health of exposed workers.

Bosutinib Therapy Ameliorates Lung Inflammation and Fibrosis in Experimental Silicosis

Silicosis is an occupational lung disease for which no effective therapy exists. We hypothesized that bosutinib, a tyrosine kinase inhibitor, might ameliorate inflammatory responses, attenuate pulmonary fibrosis, and thus improve lung function in experimental silicosis. For this purpose, we investigated the potential efficacy of bosutinib in the treatment of experimental silicosis induced in C57BL/6 mice by intratracheal administration of silica particles. After 15 days, once disease was established, animals were randomly assigned to receive DMSO or bosutinib (1 mg/kg/dose in 0.1 mL 1% DMSO) by oral gavage, twice daily for 14 days. On day 30, lung mechanics and morphometry, total and differential cell count in alveolar septa and granuloma, levels of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, interferon (IFN)-γ, IL-4, transforming growth factor (TGF)-β, and vascular endothelial growth factor in lung homogenate, M1 and M2 macrophages, total leukocytes, and T cells in BALF, lymph nodes, and thymus, and collagen fiber content in alveolar septa and granuloma were analyzed. In a separate in vitro experiment, RAW264.7 macrophages were exposed to silica particles in the presence or absence of bosutinib. After 24 h, gene expressions of arginase-1, IL-10, IL-12, inducible nitric oxide synthase (iNOS), metalloproteinase (MMP)-9, tissue inhibitor of metalloproteinase (TIMP)-1, and caspase-3 were evaluated. In vivo, in silicotic animals, bosutinib, compared to DMSO, decreased: (1) fraction area of collapsed alveoli, (2) size and number of granulomas, and mononuclear cell granuloma infiltration; (3) IL-1β, TNF-α, IFN-γ, and TGF-β levels in lung homogenates, (4) collagen fiber content in lung parenchyma, and (5) viscoelastic pressure and static lung elastance. Bosutinib also reduced M1 cell counts while increasing M2 macrophage population in both lung parenchyma and granulomas. Total leukocyte, regulatory T, CD4⁺, and CD8⁺ cell counts in the lung-draining lymph nodes also decreased with bosutinib therapy without affecting thymus cellularity. In vitro, bosutinib led to a decrease in IL-12 and iNOS and increase in IL-10, arginase-1, MMP-9, and TIMP-1. In conclusion, in the current model of silicosis, bosutinib therapy yielded beneficial effects on lung inflammation and remodeling, therefore resulting in lung mechanics improvement. Bosutinib may hold promise for silicosis; however, further studies are required.

Survival following lung transplantation for artificial stone silicosis relative to idiopathic pulmonary fibrosis

BACKGROUND

Silicosis is a progressive lung disease resulting from the inhalation of respirable crystalline silica. Lung transplantation is the only treatment for end-stage silicosis. The aim of this study was to analyze the survival experience following lung transplantation among patients with silicosis.

METHODS

We reviewed data for all patients who underwent lung transplantation for silicosis and a matched group undergoing lung transplantation for idiopathic pulmonary fibrosis (IPF) at a single medical center between March 2006 and the end of December 2013. Survival was followed through 2015.

RESULTS

A total of 17 lung transplantations were performed for silicosis among 342 lung transplantations (4.9%) during the study period. We observed non-statistically significant survival advantage (hazard ratio 0.6; 95%CI 0.24-1.55) for those undergoing lung transplantation for silicosis relative to IPF patients undergoing lung transplantation during the same period.

CONCLUSIONS

Within the limits of a small sample, survival in silicosis patients following lung transplantation was not reduced compared to IPF. Am. J. Ind. Med. 60:248-254, 2017. © 2017 Wiley Periodicals, Inc.

Cell-Based Therapy for Silicosis

Silicosis is the most common pneumoconiosis globally, with higher prevalence and incidence in developing countries. To date, there is no effective treatment to halt or reverse the disease progression caused by silica-induced lung injury. Significant advances have to be made in order to reduce morbidity and mortality related to silicosis. In this review, we have highlighted the main mechanisms of action that cause lung damage by silica particles and summarized the data concerning the therapeutic promise of cell-based therapy for silicosis.

Dasatinib Reduces Lung Inflammation and Fibrosis in Acute Experimental Silicosis

Silicosis is an occupational lung disease with no effective treatment. We hypothesized that dasatinib, a tyrosine kinase inhibitor, might exhibit therapeutic efficacy in silica-induced pulmonary fibrosis. Silicosis was induced in C57BL/6 mice by a single intratracheal administration of silica particles, whereas the control group received saline. After 14 days, when the disease was already established, animals were randomly assigned to receive DMSO or dasatinib (1 mg/kg) by oral gavage, twice daily, for 14 days. On day 28, lung morphofunction, inflammation, and remodeling were investigated. RAW 264.7 cells (a macrophage cell line) were incubated with silica particles, followed by treatment or not with dasatinib, and evaluated for macrophage polarization. On day 28, dasatinib improved lung mechanics, increased M2 macrophage counts in lung parenchyma and granuloma, and was associated with reduction of fraction area of granuloma, fraction area of collapsed alveoli, protein levels of tumor necrosis factor-α, interleukin-1β, transforming growth factor-β, and reduced neutrophils, M1 macrophages, and collagen fiber content in lung tissue and granuloma in silicotic animals. Additionally, dasatinib reduced expression of iNOS and increased expression of arginase and metalloproteinase-9 in silicotic macrophages. Dasatinib was effective at inducing macrophage polarization toward the M2 phenotype and reducing lung inflammation and fibrosis, thus improving lung mechanics in a murine model of acute silicosis.

Mesenchymal stem cells use extracellular vesicles to outsource mitophagy and shuttle microRNAs

Mesenchymal stem cells (MSCs) and macrophages are fundamental components of the stem cell niche and function coordinately to regulate haematopoietic stem cell self-renewal and mobilization. Recent studies indicate that mitophagy and healthy mitochondrial function are critical to the survival of stem cells, but how these processes are regulated in MSCs is unknown. Here we show that MSCs manage intracellular oxidative stress by targeting depolarized mitochondria to the plasma membrane via arrestin domain-containing protein 1-mediated microvesicles. The vesicles are then engulfed and re-utilized via a process involving fusion by macrophages, resulting in enhanced bioenergetics. Furthermore, we show that MSCs simultaneously shed micro RNA-containing exosomes that inhibit macrophage activation by suppressing Toll-like receptor signalling, thereby de-sensitizing macrophages to the ingested mitochondria. Collectively, these studies mechanistically link mitophagy and MSC survival with macrophage function, thereby providing a physiologically relevant context for the innate immunomodulatory activity of MSCs.

Silica Triggers Inflammation and Ectopic Lymphoid Neogenesis in the Lungs in Parallel with Accelerated Onset of Systemic Autoimmunity and Glomerulonephritis in the Lupus-Prone NZBWF1 Mouse

Genetic predisposition and environmental factors influence the development of human autoimmune disease. Occupational exposure to crystalline silica (cSiO₂) has been etiologically linked to increased incidence of autoimmunity, including systemic lupus erythematosus (SLE), but the underlying mechanisms are poorly understood. The purpose of this study was to test the hypothesis that early repeated short-term cSiO₂ exposure will modulate both latency and severity of autoimmunity in the lupus-prone female NZBWF1 mouse. Weekly intranasal exposure to cSiO₂ (0.25 and 1.0 mg) for 4 wk beginning at 9 wk of age both reduced latency and increased intensity of glomerulonephritis. cSiO₂ elicited robust inflammatory responses in the lungs as evidenced by extensive perivascular and peribronchial lymphoplasmacytic infiltration consisting of IgG-producing plasma cells, and CD45R+ and CD3+ lymphocytes that were highly suggestive of ectopic lymphoid tissue (ELT). In addition, there were elevated concentrations of immunoglobulins and the cytokines MCP-1, TNF-α and IL-6 in bronchoalveolar lavage fluid. cSiO₂-associated kidney and lung effects paralleled dose-dependent elevations of autoantibodies and proinflammatory cytokines in plasma. Taken together, cSiO₂-induced pulmonary inflammation and ectopic lymphoid neogenesis in the NZBWF1 mouse corresponded closely to systemic inflammatory and autoimmune responses as well as the early initiation of pathological outcomes in the kidney. These findings suggest that following airway exposure to crystalline silica, in mice genetically prone to SLE, the lung serves as a platform for triggering systemic autoimmunity and glomerulonephritis.

Association between inflammatory biomarkers in plasma, radiological severity, and duration of exposure in patients with silicosis

OBJECTIVE

To evaluate the plasma levels of CCL2, CCL3, CCL11, CCL24, tumor necrosis factor alpha, sTNFR1, and sTNFR2 in subjects exposed to silica (SES) with and without silicosis compared with unexposed reference control group, and their associations with the radiological severity and duration of exposure to silica.

METHODS

Fifty-seven SES; 36 with silicosis and 22 subjects in control group, were included in the study.

RESULTS

CCL3, CCL24, sTNFR1, and sTNFR2 were increased in SES and in SES with silicosis than in controls. There were no differences in the levels of CCL2, CCL11, or tumor necrosis factor alpha. The sTNFR2 level was greater in SES with silicosis than in SES without silicosis. There was a positive correlation between sTNFR1 and sTNFR2 and the radiological severity and time of exposure to silica. sTNFR2 was associated with all categories of radiological severity.

CONCLUSION

sTNFR2 is associated with silicosis severity and early exposure to silica.

Loss of monocyte chemoattractant protein-1 alters macrophage polarization and reduces NFκB activation in the foreign body response

Implantation of biomaterials elicits a foreign body response characterized by fusion of macrophages to form foreign body giant cells and fibrotic encapsulation. Studies of the macrophage polarization involved in this response have suggested that alternative (M2) activation is associated with more favorable outcomes. Here we investigated this process in vivo by implanting mixed cellulose ester filters or polydimethylsiloxane disks in the peritoneal cavity of wild-type (WT) and monocyte chemoattractant protein-1 (MCP-1) knockout mice. We analyzed classical (M1) and alternative (M2) gene expression via quantitative polymerase chain reaction, immunohistochemistry and enzyme-linked immunosorbent assay in both non-adherent cells isolated by lavage and implant-adherent cells. Our results show that macrophages undergo unique activation that displays features of both M1 and M2 polarization including induction of tumor necrosis factor α (TNF), which induces the expression and nuclear translocation of p50 and RelA determined by immunofluorescence and Western blot. Both processes were compromised in fusion-deficient MCP-1 KO macrophages in vitro and in vivo. Furthermore, inclusion of BAY 11-7028, an inhibitor of NFκB activation, reduced nuclear translocation of RelA and fusion in WT macrophages. Our studies suggest that peritoneal implants elicit a unique macrophage polarization phenotype leading to induction of TNF and activation of the NFκB pathway.

Case of accelerated silicosis in a sandblaster

Sandblasting is traditionally known as a high-risk profession for potential development of lung silicosis. Reported is a case of a sandblaster with confirmed accelerated silicosis, a condition rather rarely diagnosed in the Czech Republic. Initially, the patient presented with progressive dry cough and exertional dyspnoea. In the early diagnostic process, a possible occupational aetiology was considered given his occupational history and known high-risk exposure to respirable silica particles confirmed by industrial hygiene assessment at the patient's workplace. The condition was confirmed by clinical, histological and autopsy findings. The patient died during lung transplantation, less than five years from diagnosis.

P2X7 receptor modulates inflammatory and functional pulmonary changes induced by silica

Silicosis is an occupational lung disease, characterized by irreversible and progressive fibrosis. Silica exposure leads to intense lung inflammation, reactive oxygen production, and extracellular ATP (eATP) release by macrophages. The P2X7 purinergic receptor is thought to be an important immunomodulator that responds to eATP in sites of inflammation and tissue damage. The present study investigates the role of P2X7 receptor in a murine model of silicosis. To that end wild-type (C57BL/6) and P2X7 receptor knockout mice received intratracheal injection of saline or silica particles. After 14 days, changes in lung mechanics were determined by the end-inflation occlusion method. Bronchoalveolar lavage and flow cytometry analyzes were performed. Lungs were harvested for histological and immunochemistry analysis of fibers content, inflammatory infiltration, apoptosis, as well as cytokine and oxidative stress expression. Silica particle effects on lung alveolar macrophages and fibroblasts were also evaluated in cell line cultures. Phagocytosis assay was performed in peritoneal macrophages. Silica exposure increased lung mechanical parameters in wild-type but not in P2X7 knockout mice. Inflammatory cell infiltration and collagen deposition in lung parenchyma, apoptosis, TGF-β and NF-κB activation, as well as nitric oxide, reactive oxygen species (ROS) and IL-1β secretion were higher in wild-type than knockout silica-exposed mice. In vitro studies suggested that P2X7 receptor participates in silica particle phagocytosis, IL-1β secretion, as well as reactive oxygen species and nitric oxide production. In conclusion, our data showed a significant role for P2X7 receptor in silica-induced lung changes, modulating lung inflammatory, fibrotic, and functional changes.

Lung transplantation in idiopathic pulmonary fibrosis: a systematic review of the literature

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a distinct form of interstitial pneumonia with unknown origin and poor prognosis. Current pharmacologic treatments are limited and lung transplantation is a viable option for appropriate patients. The aim of this review was to summarize lung transplantation survival in IPF patients overall, between single (SLT) vs. bilateral lung transplantation (BLT), pre- and post Lung Allocation Score (LAS), and summarize wait-list survival.

METHODS

A systematic review of English-language studies published in Medline or Embase between 1990 and 2013 was performed. Eligible studies were those of observational design reporting survival post-lung transplantation or while on the wait list among IPF patients.

RESULTS

Median survival post-transplantation among IPF patients is estimated at 4.5 years. From ISHLT and OPTN data, one year survival ranged from 75% - 81%; 3-year: 59% - 64%; and 5-year: 47% - 53%. Post-transplant survival is lower for IPF vs. other underlying pre-transplant diagnoses. The proportion of IPF patients receiving BLT has steadily increased over the last decade and a half. Unadjusted analyses suggest improved long-term survival for BLT vs. SLT; after adjustment for patient characteristics, the differences tend to disappear. IPF patients account for the largest proportion of patients on the wait list and while wait list time has decreased, the number of transplants for IPF patients has increased over time. OPTN data show that wait list mortality is higher for IPF patients vs. other diagnoses. The proportion of IPF patients who died while awaiting transplantation ranged from 14% to 67%. While later transplant year was associated with increased survival, no significant differences were noted pre vs. post LAS implementation; however a high LAS vs low LAS was associated with decreased one-year survival.

CONCLUSIONS

IPF accounts for the largest proportion of patients awaiting lung transplants, and IPF is associated with higher wait-list and post-transplant mortality vs. other diagnoses. Improved BLT vs. SLT survival may be the result of selection bias. Survival pre- vs. post LAS appears to be similar except for IPF patients with high LAS, who have lower survival compared to pre-LAS. Data on post-transplant morbidity outcomes are sparse.

Uncoupling between inflammatory and fibrotic responses to silica: evidence from MyD88 knockout mice

The exact implication of innate immunity in granuloma formation and irreversible lung fibrosis remains to be determined. In this study, we examined the lung inflammatory and fibrotic responses to silica in MyD88-knockout (KO) mice. In comparison to wild-type (WT) mice, we found that MyD88-KO animals developed attenuated lung inflammation, neutrophil accumulation and IL-1β release in response to silica. Granuloma formation was also less pronounced in MyD88-KO mice after silica. This limited inflammatory response was not accompanied by a concomitant attenuation of lung collagen accumulation after silica. Histological analyses revealed that while pulmonary fibrosis was localized in granulomas in WT animals, it was diffusely distributed throughout the parenchyma in MyD88-KO mice. Robust collagen accumulation was also observed in mice KO for several other components of innate immunity (IL-1R, IL-1, ASC, NALP3, IL-18R, IL-33R, TRIF, and TLR2-3-4,). We additionally show that pulmonary fibrosis in MyD88-KO mice was associated with the accumulation of pro-fibrotic regulatory T lymphocytes (T regs) and pro-fibrotic cytokine expression (TGF-β, IL-10 and PDGF-B), not with T helper (Th) 17 cell influx. Our findings indicate that the activation of MyD88-related innate immunity is central in the establishment of particle-induced lung inflammatory and granuloma responses. The development of lung fibrosis appears uncoupled from inflammation and may be orchestrated by a T reg-associated pathway.

TNFR1/phox interaction and TNFR1 mitochondrial translocation Thwart silica-induced pulmonary fibrosis

Macrophages play a fundamental role in innate immunity and the pathogenesis of silicosis. Phagocytosis of silica particles is associated with the generation of reactive oxygen species (ROS), secretion of cytokines, such as TNF, and cell death that contribute to silica-induced lung disease. In macrophages, ROS production is executed primarily by activation of the NADPH oxidase (Phox) and by generation of mitochondrial ROS (mtROS); however, the relative contribution is unclear, and the effects on macrophage function and fate are unknown. In this study, we used primary human and mouse macrophages (C57BL/6, BALB/c, and p47(phox-/-)) and macrophage cell lines (RAW 264.7 and IC21) to investigate the contribution of Phox and mtROS to silica-induced lung injury. We demonstrate that reduced p47(phox) expression in IC21 macrophages is linked to enhanced mtROS generation, cardiolipin oxidation, and accumulation of cardiolipin hydrolysis products, culminating in cell death. mtROS production is also observed in p47(phox-/-) macrophages, and p47(phox-/-) mice exhibit increased inflammation and fibrosis in the lung following silica exposure. Silica induces interaction between TNFR1 and Phox in RAW 264.7 macrophages. Moreover, TNFR1 expression in mitochondria decreased mtROS production and increased RAW 264.7 macrophage survival to silica. These results identify TNFR1/Phox interaction as a key event in the pathogenesis of silicosis that prevents mtROS formation and reduces macrophage apoptosis.

Role of di-allyl disulfide, a garlic component in NF-κB mediated transient G2-M phase arrest and apoptosis in human leukemic cell-lines

Diallyl disulfide (DADS), the major organosulfur component of processed garlic is very effective in chemoprevention of several types of cancers; however, its detailed mechanism is yet to be divulged. Present study shows antiproliferative activity of DADS against human leukemic cell-lines, mainly U937. DADS induced transient G2/M phase arrest, which is evident from FACS analysis. The results revealed that a significant transcriptional induction of p21 happened in early hours of treatment, which is due to increased nuclear translocation of NF-κB and its specific binding to p21 promoter. However, in the later hours, G2/M arrest is lost leading to apoptosis via intrinsic mitochondria-mediated pathway through generation of reactive oxygen species followed by changes in mitochondrial membrane potential. Western blots indicate release of cytochrome-c, activation of caspase-3, cleavage of PARP1, and finally decrease in bcl-2 levels. In addition, inactivation of NF-κB by its inhibitor BAY 11-7085 causes early onset of apoptosis without any transient G2/M arrest. Thus, in conclusion, DADS induces reversible G2/M arrest through NF-κB mediated pathway in human leukemic cell lines, like U937, K562, and Jurkat, lacking wild type p53. However, G2/M arrest is lost owing to the incapability of the damage repair system that leads to apoptosis.

Association between tumor necrosis factor-α 308G/A gene polymorphism and silicosis susceptibility: a meta-analysis

BACKGROUND

Tumor necrosis factor-α (TNF-α) 308 G/A gene polymorphism has been reported to be associated with susceptibility to silicosis. However, the relevant study results are still inconsistent.

OBJECTIVE AND METHODS

A meta-analysis was performed in order to drive a more precise estimation of the relationship between TNF-α-308 G/A gene polymorphism and susceptibility to silicosis. Electronic databases were searched and nine separate studies were included. The pooled odds ratios (ORs) and the corresponding 95% confidence internal (CI) were calculated by a fixed effect model.

RESULTS

A total of 1267 cases and 1214 controls were included. In the overall analysis, significantly increased silicosis risk was found (for GA+AA vs. GG OR=1.45, 95%CI: 1.20-1.760, P=1.58E4; for GA vs. GG: OR=1.53, 95%CI=1.25-1.86, P=3.11E5; for A allele vs. G allele: OR=1.27, 95%CI=1.08-1.50, P= 0.004). In the subgroup analysis, significantly increased silicosis risk was also found among Asians (for GA+AA vs. GG: OR=1.63, 95%CI=1.27-2.08, P=1.01E4), for GA vs. GG: OR=1.71, 95%CI=1.33-2.20, P=3.44E5), for A allele vs. G allele: OR=1.45, 95%CI=1.17-1.80, P=0.001). However, no significantly increased risk was found among non-Asians for all genetic models.

CONCLUSIONS

TNF-α-308 G/A polymorphism might lead to an increased risk of silicosis susceptibility, especially for Asians. However, further studies with large sample sizes should be conducted to confirm the association.

Differential response of primary alveolar type I and type II cells to LPS stimulation

The alveolar epithelium serves as a barrier between organism and environment and functions as the first line of protection against potential respiratory pathogens. Alveolar type II (TII) cells have traditionally been considered the immune cells of the alveolar epithelium, as they possess immunomodulatory functions; however, the precise role of alveolar type I (TI) cells, which comprise ∼95% of the alveolar epithelial surface area, in lung immunity is not clear. We sought to determine if there was a difference in the response of TI and TII cells to lung injury and if TI cells could actively participate in the alveolar immune response. TI cells isolated via fluorescence activated cell sorting (FACS) from LPS-injured rats demonstrated greater fold-induction of multiple inflammatory mediators than TII cells isolated in the same manner from the same animals. Levels of the cytokines TNF-α, IL-6 and IL-1β from cultured primary rat TI cells after LPS stimulation were significantly increased compared to similarly studied primary rat TII cells. We found that contrary to published reports, cultured TII cells produce relatively small amounts of TNF-α, IL-6 and IL-1β after LPS treatment; the higher levels of cytokine expression from cultured TII cells reported in the literature were likely from macrophage contamination due to traditional non-FACS TII cell isolation methods. Co-culture of TII cells with macrophages prior to LPS stimulation increased TNF-α and IL-6 production to levels reported by other investigators for TII cells, however, co-culture of TI cells and macrophages prior to LPS treatment resulted in marked increases in TNF-α and IL-6 production. Finally, exogenous surfactant blunted the IL-6 response to LPS in cultured TI cells. Taken together, these findings advocate a role for TI cells in the innate immune response and suggest that both TI and TII cells are active players in host defense mechanisms in the lung.

Regular exercise training attenuates pulmonary inflammatory responses to inhaled alumina refinery dust in mice

Exposure to alumina dust has been recently associated with impaired lung mechanics and inflammation. We aimed at evaluating if moderate exercise training prevents these outcomes. Twenty-three female BALB/c mice (25-30g) were randomly divided in two main groups: control (C) and exercise (E), which were submitted, or not, to 15min of swimming, 5 days/week during 4 weeks. Then, the animals were exposed for 1h to either saline solution (CS or ES) or to a suspension of 8mg/m(3) of alumina dust (CA or EA). Twenty-four hours later pulmonary mechanics was determined by the end-inflation occlusion method. Left lungs were prepared for histology and right lungs for TGF-β determination. Static elastance increased after alumina dust exposure independently of swimming. In CA group the viscoelastic component of elastance, the viscoelastic/inhomogeneous pressure, the polymorphonuclear amount, the fraction area of alveolar collapse and TGF-β increased. Thus, exercise training may mitigate the pro-inflammatory response to inhaled aluminum refinery dust.

Silicosis

Silicosis is a fibrotic lung disease caused by inhalation of free crystalline silicon dioxide or silica. Occupational exposure to respirable crystalline silica dust particles occurs in many industries. Phagocytosis of crystalline silica in the lung causes lysosomal damage, activating the NALP3 inflammasome and triggering the inflammatory cascade with subsequent fibrosis. Impairment of lung function increases with disease progression, even after the patient is no longer exposed. Diagnosis of silicosis needs carefully documented records of occupational exposure and radiological features, with exclusion of other competing diagnoses. Mycobacterial diseases, airway obstruction, and lung cancer are associated with silica dust exposure. As yet, no curative treatment exists, but comprehensive management strategies help to improve quality of life and slow deterioration. Further efforts are needed for recognition and control of silica hazards, especially in developing countries.

Autocrine abscisic acid plays a key role in quartz-induced macrophage activation

Inhalation of quartz induces silicosis, a lung disease where alveolar macrophages release inflammatory mediators, including prostaglandin-E(2) (PGE(2)) and tumor necrosis factor α (TNF-α). Here we report the pivotal role of abscisic acid (ABA), a recently discovered human inflammatory hormone, in silica-induced activation of murine RAW264.7 macrophages and of rat alveolar macrophages (AMs). Stimulation of both RAW264.7 cells and AMs with quartz induced a significant increase of ABA release (5- and 10-fold, respectively), compared to untreated cells. In RAW264.7 cells, autocrine ABA released after quartz stimulation sequentially activates the plasma membrane receptor LANCL2 and NADPH oxidase, generating a Ca(2+) influx resulting in NFκ B nuclear translocation and PGE(2) and TNF-α release (3-, 2-, and 3.5-fold increase, respectively, compared to control, unstimulated cells). Quartz-stimulated RAW264.7 cells silenced for LANCL2 or preincubated with a monoclonal antibody against ABA show an almost complete inhibition of NFκ B nuclear translocation and PGE(2) and TNF-α release compared to controls electroporated with a scramble oligonucleotide or preincubated with an unrelated antibody. AMs showed similar early and late ABA-induced responses as RAW264.7 cells. These findings identify ABA and LANCL2 as key mediators in quartz-induced inflammation, providing possible new targets for antisilicotic therapy.

Survival following lung transplantation for silicosis and other occupational lung diseases

BACKGROUND

Information is scant assessing outcomes in lung transplantation (LT) in advanced occupational lung diseases (OLD).

AIMS

To analyse survival after LT for OLD.

METHODS

Using data from the US Organ Procurement and Transplantation Network Registry (OPTN-R), we identified subjects aged ≥ 18 years transplanted for OLD from 2005 to 2010. OPTN-R selected referents of corresponding age, sex and body mass index (BMI) who underwent LT for other diagnoses were also identified. Post-LT survival time was estimated with Cox proportional hazard models. Baseline age, BMI, forced expiratory volume in 1 s, creatinine, lung allocation score, donor age, donor lung ischaemic time and transplant type (single versus bilateral) were included as covariates. Time-dependent covariates were used to model differences in relative risk over time.

RESULTS

Thirty-seven males underwent LT for silicosis (n = 19) or other OLD (n = 18) during the analytic period (0.5% of all LTs). For non-silicotic OLD, 6-month and 1- and 3-year survival estimates were 66, 55 and 55%, compared with the silicotic group (86, 86 and 76%) and referent group (89, 84 and 67%). During the first year post-transplant, those with OLD (silicosis and others combined) manifested an overall 2-fold increased mortality risk [hazard ratio (HR) 2.3, 95% CI 1.3-4.4; P < 0.05] compared to referents. In stratified analysis, this increased risk of death was restricted to those with non-silicotic OLD (HR 3.1, 95% CI 1.5-6.6; P < 0.01). Poorer survival was limited to the first year post-LT.

CONCLUSIONS

Subjects undergoing LT for OLD other than silicosis may be at increased risk of death in the first year post-transplantation.

Yin yang 1 is a novel regulator of pulmonary fibrosis

RATIONALE

The differentiation of fibroblasts into myofibroblasts is a cardinal feature of idiopathic pulmonary fibrosis (IPF). The transcription factor Yin Yang 1 (YY1) plays a role in the proliferation and differentiation of diverse cell types, but its role in fibrotic lung diseases is not known.

OBJECTIVES

To elucidate the mechanism by which YY1 regulates fibroblast differentiation and lung fibrosis.

METHODS

Lung fibroblasts were cultured with transforming growth factor (TGF)-β or tumor necrosis factor-α. Nuclear factor (NF)-κB, YY1, and α-smooth muscle actin (SMA) were determined in protein, mRNA, and promoter reporter level. Lung fibroblasts and lung fibrosis were assessed in a partial YY1-deficient mouse and a YY1(f/f) conditional knockout mouse after being exposed to silica or bleomycin.

MEASUREMENTS AND MAIN RESULTS

TGF-β and tumor necrosis factor-α up-regulated YY1 expression in lung fibroblasts. TGF-β-induced YY1 expression was dramatically decreased by an inhibitor of NF-κB, which blocked I-κB degradation. YY1 is significantly overexpressed in both human IPF and murine models of lung fibrosis, including in the aggregated pulmonary fibroblasts of fibrotic foci. Furthermore, the mechanism of fibrogenesis is that YY1 can up-regulate α-SMA expression in pulmonary fibroblasts. YY1-deficient (YY1(+/-)) mice were significantly protected from lung fibrosis, which was associated with attenuated α-SMA and collagen expression. Finally, decreasing YY1 expression through instilled adenovirus-cre in floxed-YY1(f/f) mice reduced lung fibrosis.

CONCLUSIONS

YY1 is overexpressed in fibroblasts in both human IPF and murine models in a NF-κB-dependent manner, and YY1 regulates fibrogenesis at least in part by increasing α-SMA and collagen expression. Decreasing YY1 expression may provide a new therapeutic strategy for pulmonary fibrosis.

Novel role of AMP-activated protein kinase signaling in cigarette smoke induction of IL-8 in human lung epithelial cells and lung inflammation in mice

Cigarette smoke (CS) increases chemokine production in lung epithelial cells (LECs), but the pathways involved are not completely understood. AMP-activated protein kinase (AMPK), a crucial regulator of energy homeostasis, may modulate inflammation. Here, we show that cigarette smoke extract sequentially activated NADPH oxidase; increased intracellular reactive oxygen species (ROS) level; activated AMPK, NF-κB, and STAT3; and induced interleukin 8 (IL-8) in human LECs. Inhibition of NADPH oxidase activation by apocynin or siRNA targeting p47(phox) (a subunit of NADPH oxidase) attenuated the increased intracellular ROS level, AMPK activation, and IL-8 induction. Removal of intracellular ROS by N-acetylcysteine reduced the AMPK activation and IL-8 induction. Prevention of AMPK activation by Compound C or AMPK siRNA lessened the activation of both NF-κB and STAT3 and the induction of IL-8. Abrogation of the activation of NF-κB and STAT3 by BAY11-7085 and AG490, respectively, attenuated the IL-8 induction. We additionally show that chronic CS exposure in mice promoted AMPK phosphorylation and expression of MIP-2α (an IL-8 homolog) in LECs and lungs, as well as lung inflammation, all of which were reduced by Compound C treatment. Thus, a novel NADPH oxidase-dependent, ROS-sensitive AMPK signaling is important for CS-induced IL-8 production in LECs and possibly lung inflammation.