Macrophage-mediated inflammation and disease: a focus on the lung

Synergistic effects of mesenchymal stem cell-derived extracellular vesicles and dexamethasone on macrophage polarization under inflammatory conditions

The undesirable inflammation and the excessive M1 macrophage activity may lead to inflammatory diseases. Corticosteroids and stem cell therapy are used in clinical practice to promote anti-inflammatory responses. However, this protocol has limitations and is associated with numerous side effects. In this study, the synergistic anti-inflammatory effects of dexamethasone (Dex) and mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) were evaluated to enhance the polarization of M1 inflammatory macrophages into the anti-inflammatory (M2) phenotype. Hence, we designed different combinations of Dex and EVs using three methods, including EVs isolated from Dex-preconditioned MSCs (Pre-Dex-EVs), EVs loaded with Dex (L-Dex-EVs), and EVs and Dex co-administration (Dex + EVs). All designed EVs had a significant effect on reducing the expression of M1-related genes (iNOS, Stat1, and IRF5), cytokines (IL6 and TNF-a), and CD markers (CD86) in lipopolysaccharide-stimulated macrophages. On the other hand, these combinations promoted the expression of alternative-activated M2-related genes (Arg-1, Stat6, and IRF4), cytokine (IL10), and CD markers (CD206).The combination of Dex and MSC-EVs enhances the effectiveness of both and synergistically promotes the conversion of inflammatory macrophages into an anti-inflammatory state.

Inhibition of the mitochondrial pyruvate carrier simultaneously mitigates hyperinflammation and hyperglycemia in COVID-19

The relationship between diabetes and COVID-19 is bi-directional: while individuals with diabetes and high blood glucose (hyperglycemia) are predisposed to severe COVID-19, SARS-CoV-2 infection can also cause hyperglycemia and exacerbate underlying metabolic syndrome. Therefore, interventions capable of breaking the network of SARS-CoV-2 infection, hyperglycemia, and hyper-inflammation, all factors that drive COVID-19 pathophysiology, are urgently needed. Here, we show that genetic ablation or pharmacological inhibition of mitochondrial pyruvate carrier (MPC) attenuates severe disease following influenza or SARS-CoV-2 pneumonia. MPC inhibition using a second-generation insulin sensitizer, MSDC-0602 K (MSDC), dampened pulmonary inflammation and promoted lung recovery, while concurrently reducing blood glucose levels and hyperlipidemia following viral pneumonia in obese mice. Mechanistically, MPC inhibition enhanced mitochondrial fitness and destabilized HIF-1α, leading to dampened virus-induced inflammatory responses in both murine and human lung macrophages. We further showed that MSDC enhanced responses to nirmatrelvir (the antiviral component of Paxlovid) to provide high levels of protection against severe host disease development following SARS-CoV-2 infection and suppressed cellular inflammation in human COVID-19 lung autopsies, demonstrating its translational potential for treating severe COVID-19. Collectively, we uncover a metabolic pathway that simultaneously modulates pulmonary inflammation, tissue recovery, and host metabolic health, presenting a synergistic therapeutic strategy to treat severe COVID-19, particularly in patients with underlying metabolic disease.

Equine alveolar macrophages and monocyte-derived macrophages respond differently to an inflammatory stimulus

Alveolar macrophages (AMs) are the predominant innate immune cell in the distal respiratory tract. During inflammatory responses, AMs may be supplemented by blood monocytes, which differentiate into monocyte-derived macrophages (MDMs). Macrophages play important roles in a variety of common equine lower airway diseases, including severe equine asthma (SEA). In an experimental model, an inhaled mixture of Aspergillus fumigatus spores, lipopolysaccharide, and silica microspheres (FLS), induced SEA exacerbation in susceptible horses. However, whether equine AMs and MDMs have differing immunophenotypes and cytokine responses to FLS stimulation is unknown. To address these questions, alveolar macrophages/monocytes (AMMs) were isolated from bronchoalveolar lavage fluid and MDMs derived from blood of six healthy horses. Separately, AMMs and MDMs were cultured with and without FLS for six hours after which cell surface marker expression and cytokine production were analyzed by flow cytometry and a bead-based multiplex assay, respectively. Results showed that regardless of exposure conditions, AMMs had significantly higher surface expression of CD163 and CD206 than MDMs. Incubation with FLS induced secretion of IL-1β, IL-8, TNF-α and IFN-γ in AMMs, and IL-8, IL-10 and TNF-α in MDMs. These results suggest that AMMs have a greater proinflammatory response to in vitro FLS stimulation than MDMs, inferring differing roles in equine lung inflammation. Variability in recruitment and function of monocyte-macrophage populations warrant more detailed in vivo investigation in both homeostatic and diseased states.

Pulmonary Fibrosis as a Result of Acute Lung Inflammation: Molecular Mechanisms, Relevant In Vivo Models, Prognostic and Therapeutic Approaches

Pulmonary fibrosis is a chronic progressive lung disease that steadily leads to lung architecture disruption and respiratory failure. The development of pulmonary fibrosis is mostly the result of previous acute lung inflammation, caused by a wide variety of etiological factors, not resolved over time and causing the deposition of fibrotic tissue in the lungs. Despite a long history of study and good coverage of the problem in the scientific literature, the effective therapeutic approaches for pulmonary fibrosis treatment are currently lacking. Thus, the study of the molecular mechanisms underlying the transition from acute lung inflammation to pulmonary fibrosis, and the search for new molecular markers and promising therapeutic targets to prevent pulmonary fibrosis development, remain highly relevant tasks. This review focuses on the etiology, pathogenesis, morphological characteristics and outcomes of acute lung inflammation as a precursor of pulmonary fibrosis; the pathomorphological changes in the lungs during fibrosis development; the known molecular mechanisms and key players of the signaling pathways mediating acute lung inflammation and pulmonary fibrosis, as well as the characteristics of the most common in vivo models of these processes. Moreover, the prognostic markers of acute lung injury severity and pulmonary fibrosis development as well as approved and potential therapeutic approaches suppressing the transition from acute lung inflammation to fibrosis are discussed.

The Inflammasome NLR Family Pyrin Domain-Containing Protein 3 (NLRP3) as a Novel Therapeutic Target for Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a dramatic disease without cure. The US Food and Drug Administration-approved drugs, pirfenidone and nintedanib, only slow disease progression. The clinical investigation of novel therapeutic approaches for IPF is an unmet clinical need. Nucleotide-binding oligomerization domain-like receptor or NOD-like receptors are pattern recognition receptors capable of binding a large variety of stress factors. NLR family pyrin domain-containing protein 3 (NLRP3), once activated, promotes IL-1β, IL-18 production, and innate immune responses. Multiple reports indicate that the inflammasome NLRP3 is overactivated in IPF patients, leading to increased production of class I IL and collagens. Similarly, data from animal models of pulmonary fibrosis confirm the role of NLRP3 in the development of chronic lung injury and pulmonary fibrosis. This report provides a review of the evidence of NLRP3 activation in IPF and of NLRP3 inhibition in different animal models of fibrosis, and highlights the recent advances in direct and indirect NLRP3 inhibitors.

TFAM-Dependent Mitochondrial Metabolism Is Required for Alveolar Macrophage Maintenance and Homeostasis

Alveolar macrophages (AMs) are major lung tissue-resident macrophages capable of proliferating and self-renewal in situ. AMs are vital in pulmonary antimicrobial immunity and surfactant clearance. The mechanisms regulating AM compartment formation and maintenance remain to be fully elucidated currently. In this study, we have explored the roles of mitochondrial transcription factor A (TFAM)-mediated mitochondrial fitness and metabolism in regulating AM formation and function. We found that TFAM deficiency in mice resulted in significantly reduced AM numbers and impaired AM maturation in vivo. TFAM deficiency was not required for the generation of AM precursors nor the differentiation of AM precursors into AMs, but was critical for the maintenance of AM compartment. Mechanistically, TFAM deficiency diminished gene programs associated with AM proliferation and self-renewal and promoted the expression of inflammatory genes in AMs. We further showed that TFAM-mediated AM compartment impairment resulted in defective clearance of cellular debris and surfactant in the lung and increased the host susceptibility to severe influenza virus infection. Finally, we found that influenza virus infection in AMs led to impaired TFAM expression and diminished mitochondrial fitness and metabolism. Thus, our data have established the critical function of TFAM-mediated mitochondrial metabolism in AM maintenance and function.

PP2A-mTOR-p70S6K/4E-BP1 axis regulates M1 polarization of pulmonary macrophages and promotes ambient particulate matter induced mouse lung injury

To identify key signaling pathways involved in ambient particulate matter (PM)-induced pulmonary injury, we generated a mouse model with myeloid-specific deletion of Ppp2r1a gene (encoding protein phosphatase 2 A (PP2A) A subunit), and conducted experiments in a real-ambient PM exposure system. PP2A Aα^-/- homozygote (Aα HO) mice and matched wild-type (WT) littermates were exposed to PM over 3-week and 6-week. The effects of PM exposure on pulmonary inflammation, oxidative stress, and apoptosis were significantly enhanced in Aα HO compared to WT mice. The number of pulmonary macrophages increased by 74.8~88.0% and enhanced M1 polarization appeared in Aα HO mice upon PM exposure. Secretion of M1 macrophage-related inflammatory cytokines was significantly increased in Aα HO vs. WT mice following PM exposure. Moreover, we demonstrated that PP2A-B56α holoenzyme regulated M1 polarization and that the mTOR signaling pathway mediated the persistent M1 polarization upon PM2.5 exposure. Importantly, PP2A-B56α holoenzyme was shown to complex with mTOR/p70S6K/4E-BP1, and suppression of B56α led to enhanced phosphorylation of mTOR, p70S6K, and 4E-BP1. These observations demonstrate that the PP2A-mTOR-p70S6K/4E-BP1 signaling is a critical pathway in mediating macrophage M1 polarization, which contributes to PM-induced pulmonary injury.

The journey of SARS-CoV-2 in human hosts: a review of immune responses, immunosuppression, and their consequences

Coronavirus disease 2019 (COVID-19) is a highly infectious viral disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Laboratory findings from a significant number of patients with COVID-19 indicate the occurrence of leukocytopenia, specifically lymphocytopenia. Moreover, infected patients can experience contrasting outcomes depending on lymphocytopenia status. Patients with resolved lymphocytopenia are more likely to recover, whereas critically ill patients with signs of unresolved lymphocytopenia develop severe complications, sometimes culminating in death. Why immunodepression manifests in patients with COVID-19 remains unclear. Therefore, the evaluation of clinical symptoms and laboratory findings from infected patients is critical for understanding the disease course and its consequences. In this review, we take a logical approach to unravel the reasons for immunodepression in patients with COVID-19. Following the footprints of the virus within host tissues, from entry to exit, we extrapolate the mechanisms underlying the phenomenon of immunodepression.

New Insights into the Role of NLRP3 Inflammasome in Pathogenesis and Treatment of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is an inflammatory lung disease characterized by chronic airway obstruction and emphysema. Accumulating studies have shown that the onset and development of COPD are related to an aberrant immune response induced by the dysregulation of a number of genetic and environmental factors, while the exact pathogenesis of this disease is not well defined. Emerging studies based on tests on samples from COPD patients, animal models, pharmacological and genetic data suggest that the NLR family pyrin domain containing 3 (NLRP3) inflammasome activation is required in the lung inflammatory responses in the development of COPD. Although the available clinical studies targeting the inflammasome effector cytokine, IL-1β, or IL-1 signaling do not show positive outcomes for COPD treatment, many alternative strategies have been proposed by recent emerging studies. Here, we highlight the recent progress in our understanding of the role of the NLRP3 inflammasome in COPD and propose possible future studies that may further elucidate the roles of the inflammasome in the pathogenesis or the intervention of this inflammatory lung disease.

Macrophage exosomes transfer angiotensin II type 1 receptor to lung fibroblasts mediating bleomycin-induced pulmonary fibrosis

BACKGROUND

Macrophages are involved in the pathogenesis of idiopathic pulmonary fibrosis, partially by activating lung fibroblasts. However, how macrophages communicate with lung fibroblasts is largely unexplored. Exosomes can mediate intercellular communication, whereas its role in lung fibrogenesis is unclear. Here we aim to investigate whether exosomes can mediate the crosstalk between macrophages and lung fibroblasts and subsequently induce fibrosis.

METHODS

In vivo, bleomycin (BLM)-induced lung fibrosis model was established and macrophages infiltration was examined. The effects of GW4869, an exosomes inhibitor, on lung fibrosis were assessed. Moreover, macrophage exosomes were injected into mice to observe its pro-fibrotic effects. In vitro, exosomes derived from angiotensin II (Ang II)-stimulated macrophages were collected. Then, lung fibroblasts were treated with the exosomes. Twenty-four hours later, protein levels of α-collagen I, angiotensin II type 1 receptor (AT1R), transforming growth factor-β (TGF-β), and phospho-Smad2/3 (p-Smad2/3) in lung fibroblasts were examined. The Student's t test or analysis of variance were used for statistical analysis.

RESULTS

In vivo, BLM-treated mice showed enhanced infiltration of macrophages, increased fibrotic alterations, and higher levels of Ang II and AT1R. GW4869 attenuated BLM-induced pulmonary fibrosis. Mice with exosomes injection showed fibrotic features with higher levels of Ang II and AT1R, which was reversed by irbesartan. In vitro, we found that macrophages secreted a great number of exosomes. The exosomes were taken by fibroblasts and resulted in higher levels of AT1R (0.22 ± 0.02 vs. 0.07 ± 0.02, t = 8.66, P = 0.001), TGF-β (0.54 ± 0.05 vs. 0.09 ± 0.06, t = 10.00, P < 0.001), p-Smad2/3 (0.58 ± 0.06 vs. 0.07 ± 0.03, t = 12.86, P < 0.001) and α-collagen I (0.27 ± 0.02 vs. 0.16 ± 0.01, t = 7.01, P = 0.002), and increased Ang II secretion (62.27 ± 7.32 vs. 9.56 ± 1.68, t = 12.16, P < 0.001). Interestingly, Ang II increased the number of macrophage exosomes, and the protein levels of Alix (1.45 ± 0.15 vs. 1.00 ± 0.10, t = 4.32, P = 0.012), AT1R (4.05 ± 0.64 vs. 1.00 ± 0.09, t = 8.17, P = 0.001), and glyceraldehyde-3-phosphate dehydrogenase (2.13 ± 0.36 vs. 1.00 ± 0.10, t = 5.28, P = 0.006) were increased in exosomes secreted by the same number of macrophages, indicating a positive loop between Ang II and exosomes production.

CONCLUSIONS

Exosomes mediate intercellular communication between macrophages and fibroblasts plays an important role in BLM-induced pulmonary fibrosis.

FSTL1 aggravates OVA-induced inflammatory responses by activating the NLRP3/IL-1β signaling pathway in mice and macrophages

OBJECTIVE

Asthma, a well-known disease with high morbidity, is characterized by chronic airway inflammation. However, the allergic inflammation mechanisms of follistatin-like protein 1 (FSTL1) have not been elucidated. This study aims to investigate the effects of FSTL1 in ovalbumin (OVA)-induced mice and macrophages on nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3)/interleukin-1β (IL-1β) signaling pathway.

METHODS

Mice were randomly divided into control-WT, OVA-WT, control-Fstl1±, OVA-Fstl1±. Histological changes were assessed by HE and PAS staining. The protein levels of Muc-5AC, FSTL1, NLRP3, and IL-1β in lung tissue were detected by immunohistochemistry and ELISA. The bronchoalveolar lavage fluid (BALF) in mice and human serum samples were detected by ELISA. Then, mice were grouped into control, FSTL1, MCC950 + FSTL1 to further investigate the relationship between FSTL1 and NLRP3/IL-1β. Alveolar macrophage cells (MH-S cells) were separated into control, OVA, FSTL1, OVA + FSTL1, OVA + siNC, OVA + siFSTL1, MCC950, and FSTL1 + MCC950 groups to explore the effect of FSTL1 on the NLRP3/IL-1β signaling. The protein expression of NLRP3 and IL-1β in MH-S cells was detected by Western blot analysis.

RESULTS

The present results uncovered that Fstl1± significantly ameliorated OVA-induced Muc-5AC production and mucus hypersecretion. Fstl1± was also found to decrease the production of inflammatory cytokines and inflammatory cell infiltration in OVA-induced asthmatic mice. Meanwhile, the serum concentrations of FSTL1 and IL-1β were higher in  asthma subjects than the health subjects, and Fstl1± ameliorated the production of NLRP3 and IL-1β in OVA-induced asthmatic mice. Furthermore, mice by injected FSTL1 substantially stimulated the expression of NLRP3 and IL-1β, while pretreatment with MCC950 in mice significantly weakened the production of NLRP3 and IL-1β induced by injection FSTL1. Pretreatment with siFSTL1 or MCC950 significantly reduced the production of NLRP3 and IL-1β induced by OVA or FSTL1 in MH-S cells.

CONCLUSIONS

The study results showed that FSTL1 played an important role in allergic airway inflammation by activating NLRP3/IL-1β. Hence, inhibition FSTL1 could be applied as a therapeutic agent against asthma.

Uncoupling of macrophage inflammation from self-renewal modulates host recovery from respiratory viral infection

Tissue macrophages self-renew during homeostasis and produce inflammatory mediators upon microbial infection. We examined the relationship between proliferative and inflammatory properties of tissue macrophages by defining the impact of the Wnt/β-catenin pathway, a central regulator of self-renewal, in alveolar macrophages (AMs). Activation of β-catenin by Wnt ligand inhibited AM proliferation and stemness, but promoted inflammatory activity. In a murine influenza viral pneumonia model, β-catenin-mediated AM inflammatory activity promoted acute host morbidity; in contrast, AM proliferation enabled repopulation of reparative AMs and tissue recovery following viral clearance. Mechanistically, Wnt treatment promoted β-catenin-HIF-1α interaction and glycolysis-dependent inflammation while suppressing mitochondrial metabolism and thereby, AM proliferation. Differential HIF-1α activities distinguished proliferative and inflammatory AMs in vivo. This β-catenin-HIF-1α axis was conserved in human AMs and enhanced HIF-1α expression associated with macrophage inflammation in COVID-19 patients. Thus, inflammatory and reparative activities of lung macrophages are regulated by β-catenin-HIF-1α signaling, with implications for the treatment of severe respiratory diseases.

Management of Multisystem Inflammatory Syndrome in Children Associated with COVID-19 Infection

Purpose of review

The purpose of this review is to summarize what is known about multisystem inflammatory syndrome in children (MIS-C) associated with COVID-19 infection.

Recent findings

The timing of presentation and features of diagnosis are described. Cardiac involvement is common and is the focus of this review. Arrhythmias, heart block, acute heart failure, shock, cardiac dysfunction, and coronary dilation have all been reported. Therapies used to treat children with this hyperinflammation syndrome include supportive care and agents that modulate the immune system. Therapies commonly described include intravenous immunoglobulin, steroids, and cytokine-directed agents, particularly tumor necrosis factor-alpha blockade and interleukin receptor blockade. The threshold for diagnosing coronary involvement in MIS-C is coronary artery dimensions indexed to body surface that exceed the normative values (Z score >2). Those hospitalized with MIS-C are evaluated by electrocardiogram and echocardiogram; outpatient assessment by a cardiologist is indicated prior to sports clearance.

Summary

The prognosis of treated MIS-C patients is good. Future work is needed to understand the scope of cardiac involvement associated with acute COVID-19 and MIS-C in children and to define the optimal therapeutic targets for these distinct entities.

Cell-specific drug targeting in the lung

Non-targeted drug delivery systems have several limitations including the decreased bioavailability of the drug, poor stability and rapid clearance in addition to off-target distribution. Cell-specific targeted delivery approaches promise to overcome some of these limitations and enhance therapeutic selectivity. In this review, we aim to discuss cell-specific targeted approachesin the lung at the biochemical and molecular levels. These approaches include;a) directly administered small molecule drugs with intracellular action; b) targeted biologics and synthetic hybrids with extracellular action; c) site activateddrugs; and d) delivery systems.We discuss the pharmaceutical and biochemical parameters that govern the fate of drug molecules at delivery sites while presenting an overview of relevant literature surrounding this area of research and current advancements.

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

Background

Lung transplantation has been performed worldwide and admitted as an effective treatment for patients with various end-stage lung diseases. However, limit reliable clinical indicators exist to identify patients at high risk for allograft failure in lung transplant recipients. The recent advances in the knowledge of immunological aspects of the pulmonary diseases, for that innate macrophage activation, are induced by pathogen or pathogen-derived molecules and widely accepted as the critical evidence among the pathogenesis of lung inflammation and fibrosis. This study was aimed at evaluating the clinical significance of CD86- and macrophage scavenger receptor 1- (MSR1-) positive cells during the development of idiopathic pulmonary fibrosis (IPF) and pulmonary arterial hypertension (PAH), and their potential roles in the prediction of the outcomes after lung transplantation were examined.

Methods

Tissues from lung transplantation for 37 IPF and 15 PAH patients from the Department of Cardiothoracic Surgery in Wuxi People's Hospital from December 2015 to December 2016 were analyzed by immunohistochemistry (IHC) for detecting the expression and CD86 and MSR1 and correlated with clinical events after lung transplantation.

Results

IHC results showed that the expression of MSR1, IL-13, and arginase-1 (Arg1) but not CD86 in the lung section of IPF patients was dramatically enhanced when compared with that of PAH patients. The expression of MSR1, IL-13, and Arg1 but not CD86 in the lung from IPF patients with smoking was significantly increased when compared with that from nonsmoking subjects. In addition, the expression of MSR1-positive cells in IPF subjects with Klebsiella pneumoniae infection was dramatically enhanced than that in noninfection subjects. MSR1-positive macrophages were negatively associated with FEV1 and with FVC but not associated with TLC and with TL_CO. However, CD86-positive macrophages were not significantly associated with the above lung function-related factors. Furthermore, MSR1 had a higher area under the ROC curve (AUC) than CD86 for IPF diagnosis. Survival analysis indicated that high levels of MSR1-positive macrophages had a worse prognostic effect for IPF patients with lung transplantation.

Conclusion

Our study indicates the clinical significance of Klebsiella pneumoniae infection-related MSR1-positive cells in IPF progression, and it could be a prognostic marker in IPF after the lung transplant; development strategies to reduce the expression of MSR1-positive macrophages in IPF may be beneficial for the lung transplant.

Tissue-Resident Macrophages in the Control of Infection and Resolution of Inflammation

ABSTRACT

Macrophage, as an integral component of the immune system and the first responder to local damage, is on the front line of defense against infection. Over the past century, the prevailing view of macrophage origin states that all macrophage populations resided in tissues are terminally differentiated and replenished by monocytes from bone-marrow progenitors. Nonetheless, this theory has been reformed by ground-breaking discoveries from the past decades. It is now believed that tissue-resident macrophages (TRMs) are originated from the embryonic precursors and seeded in tissue prenatally. They can replenish via self-renewal throughout the lifespan. Indeed, recent studies have demonstrated that tissue-resident macrophages should not be classified by the over-simplified macrophage polarization (M1/M2) dogma during inflammation. Moreover, multiple lines of evidence have indicated that tissue-resident macrophages play critical roles in maintaining tissue homeostasis and facilitating tissue repair through controlling infection and resolving inflammation. In this review, we summarize the properties of resident macrophages in the lung, spleen, and heart, and further highlight the impact of TRM populations on inflammation control and tissue repair. We also discuss the potential role of local proliferation in maintaining a physiologically stable TRM pool in response to acute inflammation.

Identification of a nerve-associated, lung-resident interstitial macrophage subset with distinct localization and immunoregulatory properties

Tissue-resident macrophages are a diverse population of cells that perform specialized functions including sustaining tissue homeostasis and tissue surveillance. Here, we report an interstitial subset of CD169⁺ lung-resident macrophages that are transcriptionally and developmentally distinct from alveolar macrophages (AMs). They are primarily localized around the airways and are found in close proximity to the sympathetic nerves in the bronchovascular bundle. These nerve- and airway-associated macrophages (NAMs) are tissue resident, yolk sac derived, self-renewing, and do not require CCR2⁺ monocytes for development or maintenance. Unlike AMs, the development of NAMs requires CSF1 but not GM-CSF. Bulk population and single-cell transcriptome analysis indicated that NAMs are distinct from other lung-resident macrophage subsets and highly express immunoregulatory genes under steady-state and inflammatory conditions. NAMs proliferated robustly after influenza infection and activation with the TLR3 ligand poly(I:C), and in their absence, the inflammatory response was augmented, resulting in excessive production of inflammatory cytokines and innate immune cell infiltration. Overall, our study provides insights into a distinct subset of airway-associated pulmonary macrophages that function to maintain immune and tissue homeostasis.

HIV Infection Is Associated with Loss of Anti-Inflammatory Alveolar Macrophages

HIV type 1 is associated with pulmonary dysfunction that is exacerbated by cigarette smoke. Alveolar macrophages (AM) are the most prominent immune cell in the alveolar space. These cells play an important role in clearing inhaled pathogens and regulating the inflammatory environment; however, how HIV infection impacts AM phenotype and function is not well understood, in part because of their autofluorescence and the absence of well-defined surface markers. The main aim of this study was to evaluate the impact of HIV infection on human AM and to compare the effect of smoking on their phenotype and function. Time-of-flight mass cytometry and RNA sequencing were used to characterize macrophages from human bronchoalveolar lavage of HIV-infected and -uninfected smokers and nonsmokers. We found that the frequency of CD163⁺ anti-inflammatory AM was decreased, whereas CD163^-CCR7⁺ proinflammatory AM were increased in HIV infection. HIV-mediated proinflammatory polarization was associated with increased levels of inflammatory cytokines and macrophage activation. Conversely, smoking heightened the inflammatory response evident by change in the expression of CXCR4 and TLR4. Altogether, these findings suggest that HIV infection, along with cigarette smoke, favors a proinflammatory macrophage phenotype associated with enhanced expression of inflammatory molecules. Further, this study highlights time-of-flight mass cytometry as a reliable method for immunophenotyping the highly autofluorescent cells present in the bronchoalveolar lavage of cigarette smokers.

Immuno-epidemiology and pathophysiology of coronavirus disease 2019 (COVID-19)

Occasional zoonotic viral attacks on immunologically naive populations result in massive death tolls that are capable of threatening human survival. Currently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the infectious agent that causes coronavirus disease (COVID-19), has spread from its epicenter in Wuhan China to all parts of the globe. Real-time mapping of new infections across the globe has revealed that variable transmission patterns and pathogenicity are associated with differences in SARS-CoV-2 lineages, clades, and strains. Thus, we reviewed how changes in the SARS-CoV-2 genome and its structural architecture affect viral replication, immune evasion, and transmission within different human populations. We also looked at which immune dominant regions of SARS-CoV-2 and other coronaviruses are recognized by Major Histocompatibility Complex (MHC)/Human Leukocyte Antigens (HLA) genes and how this could impact on subsequent disease pathogenesis. Efforts were also placed on understanding immunological changes that occur when exposed individuals either remain asymptomatic or fail to control the virus and later develop systemic complications. Published autopsy studies that reveal alterations in the lung immune microenvironment, morphological, and pathological changes are also explored within the context of the review. Understanding the true correlates of protection and determining how constant virus evolution impacts on host-pathogen interactions could help identify which populations are at high risk and later inform future vaccine and therapeutic interventions.

Aesculetin Attenuates Alveolar Injury and Fibrosis Induced by Close Contact of Alveolar Epithelial Cells with Blood-Derived Macrophages via IL-8 Signaling

Pulmonary fibrosis is a disease in which lung tissues become fibrous and thereby causes severe respiratory disturbances. Various stimuli induce infiltration of macrophages to the respiratory tract, secreting inflammatory cytokines, which subsequently leads to the development of pulmonary fibrosis. Aesculetin, a major component of the sancho tree and chicory, is known to biologically have antioxidant and anti-inflammatory effects. Human alveolar epithelial A549 cells were cultured for 24 h in conditioned media of THP-1 monocyte-derived macrophages (mCM) with 1–20 μM aesculetin. Micromolar aesculetin attenuated the cytotoxicity of mCM containing inflammatory tumor necrosis factor-α (TNF)-α and interleukin (IL)-8 as major cytokines. Aesculetin inhibited alveolar epithelial induction of the mesenchymal markers in mCM-exposed/IL-8-loaded A549 cells (≈47–51% inhibition), while epithelial markers were induced in aesculetin-treated cells subject to mCM/IL-8 (≈1.5–2.3-fold induction). Aesculetin added to mCM-stimulated A549 cells abrogated the collagen production and alveolar epithelial CXC-chemokine receptor 2 (CXCR2) induction. The production of matrix metalloproteinase (MMP) proteins in mCM-loaded A549 cells was reduced by aesculetin (≈52% reduction), in parallel with its increase in tissue inhibitor of metalloproteinases (TIMP) proteins (≈1.8-fold increase). In addition, aesculetin enhanced epithelial induction of tight junction proteins in mCM-/IL-8-exposed cells (≈2.3–2.5-fold induction). The inhalation of polyhexamethylene guanidine (PHMG) in mice accompanied neutrophil predominance in bronchoalveolar lavage fluid (BALF) and macrophage infiltration in alveoli, which was inhibited by orally administrating aesculetin to mice. Treating aesculetin to mice alleviated PHMG-induced IL-8-mediated subepithelial fibrosis and airway barrier disruption. Taken together, aesculetin may antagonize pulmonary fibrosis and alveolar epithelial barrier disruption stimulated by the infiltration of monocyte-derived macrophages, which is typical of PHMG toxicity, involving interaction of IL-8 and CXCR2. Aesculetin maybe a promising agent counteracting macrophage-mediated inflammation-associated pulmonary disorders.

Systems analysis of benign bladder disorders: insights from omics analysis

The signaling pathways and effectors that drive the response of the bladder to nonmalignant insults or injury are incompletely defined. Interrogation of biological systems has been revolutionized by the ability to generate high-content data sets that capture information on a variety of biomolecules in cells and tissues, from DNA to RNA to proteins. In oncology, such an approach has led to the identification of cancer subtypes, improved prognostic capability, and has provided a basis for precision treatment of patients. In contrast, systematic molecular characterization of benign bladder disorders has lagged behind, such that our ability to uncover novel therapeutic interventions or increase our mechanistic understanding of such conditions is limited. Here, we discuss existing literature on the application of omics approaches, including transcriptomics and proteomics, to urinary tract conditions characterized by pathological tissue remodeling. We discuss molecular pathways implicated in remodeling, challenges in the field, and aspirations for omics-based research in the future.

Terbutaline alleviates the lung injury in the neonatal rats exposed to endotoxin: Potential roles of epithelial sodium channels

Intrauterine inflammation generates inflammatory mediators that damage the developing bronchoalveolar epithelium, resulting in neonatal lung injury. Lung fluid transport disorders are the main reasons for the development of pulmonary edema, an important pathology of lung injury. Previous studies suggested that epithelial sodium channels (ENaCs) play an important role in lung fluid transport. Here, we investigated whether changes in the expression of ENaCs were observed when neonatal rat lung injury was induced by maternal exposure to endotoxin. We also examined the therapeutic effect of terbutaline nebulizer inhalation on this injury. The results showed that maternal exposure to endotoxin increased the levels of TNF-α and IL-1β in bronchoalveolar lavage fluid, suppressed α-, β-, γ-ENaC in the neonatal rat lung, and resulted in the formation of pulmonary edema on postnatal days 1 and 7. Terbutaline up-regulated the expression of β- and γ-ENaC in the distal lung after 7 days of treatment. The potential signal molecules cAMP, PKA, and CREB expressions were increased after terbutaline treatment. In summary, maternal exposure to endotoxin decreased the expression of ENaCs in neonatal rats which, in turn, may exacerbate pulmonary edema. Inhalation of the β2-adrenergic receptor agonist terbutaline improved lung liquid clearance. By increasing the expression of sodium ion channels, the effective removal of alveolar fluid provides a new way for the prevention and treatment of neonatal lung injury.

Role of the NLRP3 inflammasome in cancer

Inflammasomes are large intracellular multi-protein signalling complexes that are formed in the cytosolic compartment as an inflammatory immune response to endogenous danger signals. The formation of the inflammasome enables activation of an inflammatory protease caspase-1, pyroptosis initiation with the subsequent cleaving of the pro-inflammatory cytokines interleukin (IL)-1β and proIL-18 to produce active forms. The inflammasome complex consists of a Nod-like receptor (NLR), the adapter apoptosis-associated speck-like (ASC) protein, and Caspase-1. Dysregulation of NLRP3 inflammasome activation is involved tumor pathogenesis, although its role in cancer development and progression remains controversial due to the inconsistent findings described. In this review, we summarize the current knowledge on the contribution of the NLRP3 inflammasome on potential cancer promotion and therapy.

Substrate accumulation and extracellular matrix remodelling promote persistent upper airway disease in mucopolysaccharidosis patients on enzyme replacement therapy

Introduction

Mucopolysaccharide diseases are a group of lysosomal storage disorders caused by deficiencies of hydrolase enzymes, leading to pathological glycosaminoglycan accumulation. A number of mucopolysaccharidosis (MPS) types are characterised by severe airway disease, the aetiology of which is poorly understood. There is ongoing evidence of significant clinical disease in the long-term despite disease modifying therapeutic strategies, including enzyme-replacement therapy (ERT). To provide a better understanding of this aspect of disease, we have characterised extracellular matrix (ECM) and inflammatory alterations in adenotonsillar tissue samples from 8 MPS patients.

Methods

Adenotonsillar samples from MPS I, IVA and VI ERT treated patients and from a single enzyme naïve MPS IIIA individual were compared to non-affected control samples using quantitative immunohistochemistry, qPCR and biochemical analysis.

Results

Significantly increased lysosomal compartment size and total sulphated glycosaminoglycan (p = 0.0007, 0.02) were identified in patient samples despite ERT. Heparan sulphate glycosaminoglycan was significantly elevated in MPS I and IIIA (p = 0.002), confirming incomplete reversal of disease. Collagen IV and laminin α-5 (p = 0.002, 0.0004) staining demonstrated increased ECM deposition within the reticular and capillary network of MPS samples. No significant change in the expression of the pro-inflammatory cytokines IL-1α, IL-6 or TNF-α was seen compared to control.

Conclusion

This study suggests a role for ECM remodelling contributing to the obstructive phenotype of airway disease in MPS. Current therapeutic strategies with ERT fail to normalise these pathological alterations within adenotonsillar samples. Our findings lend novel insight into the pathological cascade of events, with primarily structural rather than inflammatory changes contributing to the continuing phenotype seen in patients despite current therapeutic regimes.

Are the immunomodulatory properties of Lactobacillus rhamnosus CRL1505 peptidoglycan common for all Lactobacilli during respiratory infection in malnourished mice?

Previously, we reported that Lactobacillus rhamnosus CRL1505 peptidoglycan (PG05) improves the innate immune response in immunocompromised-malnourished mice after Streptococcus pneumoniae infection. This study extends those previous findings by demonstrating that the dietary recovery of malnourished mice with nasal administration of PG05 improves not only the innate immune response but the respiratory and systemic adaptive humoral response as well. PG05 enhanced the Th2 response, the recovery of B cells, and the concentration and opsonophagocytic activity of anti-pneumococcal antibodies. In addition, by performing comparative studies with the peptidoglycans from lactobacilli of the same species (L. rhamnosus CRL534) or with similar immunomodulatory properties (L. plantarum CRL1506), we demonstrated here that PG05 has unique immunomodulatory properties that cannot be extended to peptidoglycans from other probiotic strains. However, the knowledge of the molecular characteristics of PG05 is indispensable to understand immunomodulatory abilities of L. rhamnosus CRL1505.

Genotype 2 Strains of Porcine Reproductive and Respiratory Syndrome Virus Dysregulate Alveolar Macrophage Cytokine Production via the Unfolded Protein Response

Porcine reproductive and respiratory syndrome virus (PRRSV) infects alveolar macrophages (AMϕ), causing dysregulated alpha interferon (IFN-α) and tumor necrosis factor alpha (TNF-α) production through a mechanism(s) yet to be resolved. Here, we show that AMϕ infected with PRRSV secreted a reduced quantity of IFN-α following exposure of the cell to synthetic double-stranded RNA (dsRNA). This reduction did not correlate with reduced IFNA1 gene transcription. Rather, it coincided with two events that occurred late during infection and that were indicative of translational attenuation, specifically, the activation of eukaryotic translation initiation factor 2α (eIF2α) and the appearance of stress granules. Notably, the typical rapid production of TNF-α by AMϕ exposed to lipopolysaccharide (LPS) was suppressed or enhanced by PRRSV, depending on when the LPS exposure occurred after virus infection. If exposure was delayed until 6 h postinfection (hpi) so that the development of the cytokine response coincided with the time in which phosphorylation of eIF2α by the stress sensor PERK (protein kinase RNA [PKR]-like ER kinase) occurred, inhibition of TNF-α production was observed. However, if LPS exposure occurred at 2 hpi, prior to a detectable onset of eIF2α phosphorylation, a synergistic response was observed due to the earlier NF-κB activation via the stress sensor IRE1α (inositol-requiring kinase 1α). These results suggest that the asynchronous actions of two branches of the unfolded protein response (UPR), namely, IRE1α, and PERK, activated by ER stress resulting from the virus infection, are associated with enhancement or suppression of TNF-α production, respectively.IMPORTANCE The activation of AMϕ is controlled by the microenvironment to deter excessive proinflammatory cytokine responses to microbes that could impair lung function. However, viral pneumonias frequently become complicated by secondary bacterial infections, triggering severe inflammation, lung dysfunction, and death. Although dysregulated cytokine production is considered an integral component of the exacerbated inflammatory response in viral-bacterial coinfections, the mechanism responsible for this event is unknown. Here, we show that PRRSV replication in porcine AMϕ triggers activation of the IRE1α branch of the UPR, which causes a synergistic TNF-α response to LPS exposure. Thus, the severe pneumonias typically observed in pigs afflicted with PRRSV-bacterial coinfections could result from dysregulated, overly robust TNF-α production in response to opportunistic pathogens that is not commensurate with the typical restrained reaction by uninfected AMϕ. This notion could help in the design of therapies to mitigate the severity of viral and bacterial coinfections.

Spleen tyrosine kinase inhibition ameliorates airway inflammation through modulation of NLRP3 inflammosome and Th17/Treg axis

Repeated exposure to the fungal pathogen Aspergillus fumigates triggers spleen tyrosine kinase (SYK) signalling through dectin-1 activation, which is associated with deleterious airway inflammation. β-Glucan-induced dectin-1 signalling activates the NLRP3 inflammasome, which in turn rapidly produces IL-1β, a master regulator of inflammation. IL-1β expression results in Th17/Treg imbalance, pulmonary inflammation, and bystander tissue injury. This study reports that 3,4 methylenedioxy-β-nitrostyrene (MNS), a potent SYK inhibitor, markedly decreased the expression of pro-inflammatory cytokines and increased the expression of anti-inflammatory cytokines in vitro. Furthermore, SYK inhibition markedly decreased β-glucan-induced IL-1β expression, suggesting that SYK is indispensable for NLRP3 inflammasome activation. Decreased IL-1β expression correlated with reduced Th17 response and enhanced immunosuppressive Treg response. Notably, SYK inhibition ameliorated inflammation caused by repeated intranasal β-glucan challenge in BALB/C mice. SYK inhibition also restored the Th17/Treg balance via decreased Th17 and increased Treg responses, as evidenced by decreased IL-17 and ror-γ levels. Additionally, inhibition of SYK increased IL-10 secreting CD4⁺FOXP3⁺ T cells that accompanied reduced T cell proliferation. Decreased IgA in the Bronchoalveolar lavage (BAL) fluid and serum also indicated the immunosuppressive potential of SYK inhibition. Histopathology data revealed that repeated β-glucan challenge caused substantial pulmonary damage, as indicated by septal thickening and interstitial lymphocytic, neutrophil and granulocyte recruitment. These processes were effectively prevented by SYK inhibition, resulting in lung protection. Collectively, our findings suggest that SYK inhibition ameliorates dectin-1- mediated detrimental pulmonary inflammation and subsequent tissue damage. Therefore, SYK can be a new target gene in the therapeutic approach against fungal induced airway inflammation.

Macrophages: Their role, activation and polarization in pulmonary diseases

Macrophages, circulating in the blood or concatenated into different organs and tissues constitute the first barrier against any disease. They are foremost controllers of both innate and acquired immunity, healthy tissue homeostasis, vasculogenesis and congenital metabolism. Two hallmarks of macrophages are diversity and plasticity due to which they acquire a wobbling array of phenotypes. These phenotypes are appropriately synchronized responses to a variety of different stimuli from either the tissue microenvironment or - microbes or their products. Based on the phenotype, macrophages are classified into classically activated/(M1) and alternatively activated/(M2) which are further sub-categorized into M2a, M2b, M2c and M2d based upon gene expression profiles. Macrophage phenotype metamorphosis is the regulating factor in initiation, progression, and termination of numerous inflammatory diseases. Several transcriptional factors and other factors controlling gene expression such as miRNAs contribute to the transformation of macrophages at different points in different diseases. Understanding the mechanisms of macrophage polarization and modulation of their phenotypes to adjust to the micro environmental conditions might provide us a great prospective for designing novel therapeutic strategy. In view of the above, this review summarises the activation of macrophages, the factors intricated in activation along with benefaction of macrophage polarization in response to microbial infections, pulmonary toxicity, lung injury and other inflammatory diseases such as chronic obstructive pulmonary dysplasia (COPD), bronchopulmonary dysplasia (BPD), asthma and sepsis, along with the existing efforts to develop therapies targeting this facet of macrophage biology.

Phenotypic and genetic aspects of epithelial barrier function in asthmatic patients

The bronchial epithelium is continuously exposed to a multitude of noxious challenges in inhaled air. Cellular contact with most damaging agents is reduced by the action of the mucociliary apparatus and by formation of a physical barrier that controls passage of ions and macromolecules. In conjunction with these defensive barrier functions, immunomodulatory cross-talk between the bronchial epithelium and tissue-resident immune cells controls the tissue microenvironment and barrier homeostasis. This is achieved by expression of an array of sensors that detect a wide variety of viral, bacterial, and nonmicrobial (toxins and irritants) agents, resulting in production of many different soluble and cell-surface molecules that signal to cells of the immune system. The ability of the bronchial epithelium to control the balance of inhibitory and activating signals is essential for orchestrating appropriate inflammatory and immune responses and for temporally modulating these responses to limit tissue injury and control the resolution of inflammation during tissue repair. In asthmatic patients abnormalities in many aspects of epithelial barrier function have been identified. We postulate that such abnormalities play a causal role in immune dysregulation in the airways by translating gene-environment interactions that underpin disease pathogenesis and exacerbation.

Comparative study of two models of combined pulmonary fibrosis and emphysema in mice

Combined pulmonary fibrosis and emphysema (CPFE) is an "umbrella term" encompassing emphysema and pulmonary fibrosis, but its pathogenesis is not known. We established two models of CPFE in mice using tracheal instillation with bleomycin (BLM) or murine gammaherpesvirus 68 (MHV-68). Experimental mice were divided randomly into four groups: A (normal control, n=6), B (emphysema, n=6), C (emphysema+MHV-68, n=24), D (emphysema+BLM, n=6). Group C was subdivided into four groups: C1 (sacrificed on day 367, 7 days after tracheal instillation of MHV-68); C2 (day 374; 14days); C3 (day 381; 21days); C4 (day 388; 28days). Conspicuous emphysema and interstitial fibrosis were observed in BLM and MHV-68 CPFE mouse models. However, BLM induced diffuse pulmonary interstitial fibrosis with severely diffuse pulmonary inflammation; MHV-68 induced relatively modest inflammation and fibrosis, and the inflammation and fibrosis were not diffuse, but instead around bronchioles. Inflammation and fibrosis were detectable in the day-7 subgroup and reached a peak in the day-28 subgroup in the emphysema + MHV-68 group. Levels of macrophage chemoattractant protein-1, macrophage inflammatory protein-1α, interleukin-13, and transforming growth factor-β1 in bronchoalveolar lavage fluid were increased significantly in both models. Percentage of apoptotic type-2 lung epithelial cells was significantly higher; however, all four types of cytokine and number of macrophages were significantly lower in the emphysema+MHV-68 group compared with the emphysema +BLM group. The different changes in pathology between BLM and MHV-68 mice models demonstrated different pathology subtypes of CPFE: macrophage infiltration and apoptosis of type-II lung epithelial cells increased with increasing pathology score for pulmonary fibrosis.

Particulate matter exposure induces the autophagy of macrophages via oxidative stress-mediated PI3K/AKT/mTOR pathway

Many epidemiological investigations have consistently demonstrated the immunotoxicity of fine particulate matter (PM_2.5), but the underlying molecular mechanism remains unclear and needs to be elucidated. In this work, the immune cells, including pulmonary macrophages of SD rats and Raw264.7 cells, were applied to further investigate the effect of PM_2.5 on cell autophagy of macrophages, thus clarified the possible molecular mechanism of immunotoxicity caused by PM_2.5. SD rats were exposed to summer (0.2, 0.6, 1.5 mg kg^-1 b.w.) and winter (0.3, 1.5, 2.7 mg kg^-1 b.w.) PM_2.5 adopting the intratracheal instillation method. The exposure was performed one time every 3 days and continued for 2 months. The data showed that PM_2.5 exposure decreased numbers of immune cells in pulmonary macrophages of SD rats. In addition, PM_2.5 could induce the cell autophagy through the increased LC3 and decreased p62 mRNA and protein levels of pulmonary macrophages in SD rats and Raw264.7 cells in a concentration-dependent manner. Strikingly, PM_2.5-induced oxidative stress was observed. However, NAC supplement (the ROS inhibitor) significantly reversed PM_2.5-caused effects. Additionally, the PI3K/AKT/mTOR pathway was activated in PM_2.5-treated cells and NAC had an important inhibitory effect. These results demonstrated that PM_2.5 exposures induced autophagy of pulmonary macrophages via the oxidative stress-mediated PI3K/AKT/mTOR pathway, which may contribute to explain the molecular mechanism of immunotoxicity caused by PM_2.5 and provide the theoretical foundation for environment toxicology of PM_2.5.

Autophagy, TGF-β, and SMAD-2/3 Signaling Regulates Interferon-β Response in Respiratory Syncytial Virus Infected Macrophages

Human respiratory syncytial virus (RSV) is a lung tropic virus causing severe airway diseases including bronchiolitis and pneumonia among infants, children, and immuno-compromised individuals. RSV triggers transforming growth factor-β (TGF-β) production from lung epithelial cells and TGF-β facilitates RSV infection of these cells. However, it is still unknown whether RSV infected myeloid cells like macrophages produce TGF-β and the role of TGF-β if any during RSV infection of these cells. Our study revealed that RSV infected macrophages produce TGF-β and as a consequence these cells activate TGF-β dependent SMAD-2/3 signaling pathway. Further mechanistic studies illustrated a role of autophagy in triggering TGF-β production from RSV infected macrophages. In an effort to elucidate the role of TGF-β and SMAD-2/3 signaling during RSV infection, we surprisingly unfolded the requirement of TGF-β—SMAD2/3 signaling in conferring optimal innate immune antiviral response during RSV infection of macrophages. Type-I interferon (e.g., interferon-β or IFN-β) is a critical host factor regulating innate immune antiviral response during RSV infection. Our study revealed that loss of TGF-β—SMAD2/3 signaling pathway in RSV infected macrophages led to diminished expression and production of IFN-β. Inhibiting autophagy in RSV infected macrophages also resulted in reduced production of IFN-β. Thus, our studies have unfolded the requirement of autophagy—TGF-β—SMAD2/3 signaling network for optimal innate immune antiviral response during RSV infection of macrophages.

The Influence of Programmed Cell Death in Myeloid Cells on Host Resilience to Infection with Legionella pneumophila or Streptococcus pyogenes

Pathogen clearance and host resilience/tolerance to infection are both important factors in surviving an infection. Cells of the myeloid lineage play important roles in both of these processes. Neutrophils, monocytes, macrophages, and dendritic cells all have important roles in initiation of the immune response and clearance of bacterial pathogens. If these cells are not properly regulated they can result in excessive inflammation and immunopathology leading to decreased host resilience. Programmed cell death (PCD) is one possible mechanism that myeloid cells may use to prevent excessive inflammation. Myeloid cell subsets play roles in tissue repair, immune response resolution, and maintenance of homeostasis, so excessive PCD may also influence host resilience in this way. In addition, myeloid cell death is one mechanism used to control pathogen replication and dissemination. Many of these functions for PCD have been well defined in vitro, but the role in vivo is less well understood. We created a mouse that constitutively expresses the pro-survival B-cell lymphoma (bcl)-2 protein in myeloid cells (CD68(bcl2tg), thus decreasing PCD specifically in myeloid cells. Using this mouse model we explored the impact that decreased cell death of these cells has on infection with two different bacterial pathogens, Legionella pneumophila and Streptococcus pyogenes. Both of these pathogens target multiple cell death pathways in myeloid cells, and the expression of bcl2 resulted in decreased PCD after infection. We examined both pathogen clearance and host resilience and found that myeloid cell death was crucial for host resilience. Surprisingly, the decreased myeloid PCD had minimal impact on pathogen clearance. These data indicate that the most important role of PCD during infection with these bacteria is to minimize inflammation and increase host resilience, not to aid in the clearance or prevent the spread of the pathogen.

Differential pulmonary effects of CoO and La2O3 metal oxide nanoparticle responses during aerosolized inhalation in mice

BACKGROUND

Although classified as metal oxides, cobalt monoxide (CoO) and lanthanum oxide (La2O3) nanoparticles, as representative transition and rare earth oxides, exhibit distinct material properties that may result in different hazardous potential in the lung. The current study was undertaken to compare the pulmonary effects of aerosolized whole body inhalation of these nanoparticles in mice.

RESULTS

Mice were exposed to filtered air (control) and 10 or 30 mg/m(3) of each particle type for 4 days and then examined at 1 h, 1, 7 and 56 days post-exposure. The whole lung burden 1 h after the 4 day inhalation of CoO nanoparticles was 25 % of that for La2O3 nanoparticles. At 56 days post exposure, < 1 % of CoO nanoparticles remained in the lungs; however, 22-50 % of the La2O3 nanoparticles lung burden 1 h post exposure was retained at 56 days post exposure for low and high exposures. Significant accumulation of La2O3 nanoparticles in the tracheobronchial lymph nodes was noted at 56 days post exposure. When exposed to phagolysosomal simulated fluid, La nanoparticles formed urchin-shaped LaPO4 structures, suggesting that retention of this rare earth oxide nanoparticle may be due to complexation of cellular phosphates within lysosomes. CoO nanoparticles caused greater lactate dehydrogenase release in the bronchoalveolar fluid (BALF) compared to La2O3 nanoparticles at 1 day post exposure, while BAL cell differentials indicate that La2O3 nanoparticles generated more inflammatory cell infiltration at all doses and exposure points. Histopathological analysis showed acute inflammatory changes at 1 day after inhalation of either CoO or La2O3 nanoparticles. Only the 30 mg/m(3) La2O3 nanoparticles exposure caused chronic inflammatory changes and minimal fibrosis at day 56 post exposure. This is in agreement with activation of the NRLP3 inflammasome after in vitro exposure of differentiated THP-1 macrophages to La2O3 but not after CoO nanoparticles exposure.

CONCLUSION

Taken together, the inhalation studies confirmed the trend of our previous sub-acute aspiration study, which reported that CoO nanoparticles induced more acute pulmonary toxicity, while La2O3 nanoparticles caused chronic inflammatory changes and minimal fibrosis.

Control of local immunity by airway epithelial cells

The lung is ventilated by thousand liters of air per day. Inevitably, the respiratory system comes into contact with airborne microbial compounds, most of them harmless contaminants. Airway epithelial cells are known to have innate sensor functions, thus being able to detect microbial danger. To avoid chronic inflammation, the pulmonary system has developed specific means to control local immune responses. Even though airway epithelial cells can act as proinflammatory promoters, we propose that under homeostatic conditions airway epithelial cells are important modulators of immune responses in the lung. In this review, we discuss epithelial cell regulatory functions that control reactivity of professional immune cells within the microenvironment of the airways and how these mechanisms are altered in pulmonary diseases. Regulation by epithelial cells can be divided into two mechanisms: (1) mediators regulate epithelial cells' innate sensitivity in cis and (2) factors are produced that limit reactivity of immune cells in trans.

Acute Exposure to Crystalline Silica Reduces Macrophage Activation in Response to Bacterial Lipoproteins

Numerous studies have examined the relationship between alveolar macrophages (AMs) and crystalline silica (SiO2) using in vitro and in vivo immunotoxicity models; however, exactly how exposure to SiO2 alters the functionality of AM and the potential consequences for immunity to respiratory pathogens remains largely unknown. Because recognition and clearance of inhaled particulates and microbes are largely mediated by pattern recognition receptors (PRRs) on the surface of AM, we hypothesized that exposure to SiO2 limits the ability of AM to respond to bacterial challenge by altering PRR expression. Alveolar and bone marrow-derived macrophages downregulate TLR2 expression following acute SiO2 exposure (e.g., 4 h). Interestingly, these responses were dependent on interactions between SiO2 and the class A scavenger receptor CD204, but not MARCO. Furthermore, SiO2 exposure decreased uptake of fluorescently labeled Pam2CSK4 and Pam3CSK4, resulting in reduced secretion of IL-1β, but not IL-6. Collectively, our data suggest that SiO2 exposure alters AM phenotype, which in turn affects their ability to uptake and respond to bacterial lipoproteins.

Epithelial barrier function and immunity in asthma

The bronchial epithelium is constantly exposed to a wide range of environmental materials present in inhaled air, including noxious gases and anthropogenic and natural particulates, such as gas and particles from car emissions, tobacco smoke, pollens, animal dander, and pathogens. As a fully differentiated, pseudostratified mucociliary epithelium, the bronchial epithelium protects the internal milieu of the lung from these agents by forming a physical barrier involving adhesive complexes and a chemical barrier involving secretion of mucus, which traps inhaled particles that can be cleared by the mucociliary escalator. It is a testament to the effectiveness of these two barriers that most environmental challenges are largely overcome without the need to develop an inflammatory response. However, as the initial cell of contact with the environment, the bronchial epithelium also plays a pivotal role in immune surveillance and appropriate activation of immune effector cells and antigen presenting cells in the presence of pathogens or other danger signals. Thus, the bronchial epithelium plays a central role in controlling tissue homeostasis and innate immunity. This review will discuss these barrier properties and how dysregulation of these homeostatic mechanisms can contribute to disease pathologies such as asthma.

Smoking, inflammation and small cell lung cancer: recent developments

Small cell lung cancer (SCLC) accounts for 15 % of all lung tumors and represents an invasive neuroendocrine malignancy with poor survival rates. This cancer is highly prevalent in smokers and characterized by inactivation of p53 and retinoblastoma. First in vitro expansion of circulating tumor cells (CTCs) of SCLC patients allowed for investigation of the cell biology of tumor dissemination. In the suggested CTC SCLC model, the primary tumor attracts and educates tumor-promoting and immunosuppressive macrophages which in turn arm CTCs to spread and generate distal lesions. Preexisting inflammatory processes associated with chronic obstructive pulmonary disease (COPD) seem to potentiate the subsequent activity of tumor-associated macrophages (TAM). Activation of signal transducer and activator of transcription 3 (STAT3) and expression of chitinase-3-like 1/YKL-40 in SCLC CTCs seems to be associated with drug resistance. In conclusion, inflammation-associated generation of invasive and chemoresistant CTCs most likely explains the characteristic features of SCLC, namely early dissemination and rapid failure of chemotherapy.

Attenuation of Nitrogen Mustard-Induced Pulmonary Injury and Fibrosis by Anti-Tumor Necrosis Factor-α Antibody

Nitrogen mustard (NM) is a bifunctional alkylating agent that causes acute injury to the lung that progresses to fibrosis. This is accompanied by a prominent infiltration of macrophages into the lung and upregulation of proinflammatory/profibrotic cytokines including tumor necrosis factor (TNF)α. In these studies, we analyzed the ability of anti-TNFα antibody to mitigate NM-induced lung injury, inflammation, and fibrosis. Treatment of rats with anti-TNFα antibody (15 mg/kg, iv, every 9 days) beginning 30 min after intratracheal administration of NM (0.125 mg/kg) reduced progressive histopathologic alterations in the lung including perivascular and peribronchial edema, macrophage/monocyte infiltration, interstitial thickening, bronchiolization of alveolar walls, fibrin deposition, emphysema, and fibrosis. NM-induced damage to the alveolar-epithelial barrier, measured by bronchoalveolar lavage (BAL) protein and cell content, was also reduced by anti-TNFα antibody, along with expression of the oxidative stress marker, heme oxygenase-1. Whereas the accumulation of proinflammatory/cytotoxic M1 macrophages in the lung in response to NM was suppressed by anti-TNFα antibody, anti-inflammatory/profibrotic M2 macrophages were increased or unchanged. Treatment of rats with anti-TNFα antibody also reduced NM-induced increases in expression of the profibrotic mediator, transforming growth factor-β. This was associated with a reduction in NM-induced collagen deposition in the lung. These data suggest that inhibiting TNFα may represent an efficacious approach to mitigating lung injury induced by mustards.

Silica-induced inflammasome activation in macrophages: role of ATP and P2X7 receptor

Silicosis is a fibrotic lung disease caused by the inhalation of silica particles, and is considered an occupational disease, given that these particles are present in the working environment of many mining and civil construction industries. NLRP3 inflammasome activation is an important mechanism during the inflammatory process of silicosis, and it promotes the production of cytokines, such as IL-1β and IL-18. ATP also plays an important role in silicosis. Specifically, extracellular ATP can activate P2X7 receptor, which then participates in the complete assembly of the NLRP3 inflammasome and its activation. Herein, we analyze the literature to provide a better understanding of the mechanisms underlying inflammasome activation and the role of P2X7 receptors in macrophages during silicosis.

Soluble factors from Lactobacillus reuteri CRL1098 have anti-inflammatory effects in acute lung injury induced by lipopolysaccharide in mice

We have previously demonstrated that Lactobacillus reuteri CRL1098 soluble factors were able to reduce TNF-α production by human peripheral blood mononuclear cells. The aims of this study were to determine whether L. reuteri CRL1098 soluble factors were able to modulate in vitro the inflammatory response triggered by LPS in murine macrophages, to gain insight into the molecular mechanisms involved in the immunoregulatory effect, and to evaluate in vivo its capacity to exert anti-inflammatory actions in acute lung injury induced by LPS in mice. In vitro assays demonstrated that L. reuteri CRL1098 soluble factors significantly reduced the production of pro-inflammatory mediators (NO, COX-2, and Hsp70) and pro-inflammatory cytokines (TNF-α, and IL-6) caused by the stimulation of macrophages with LPS. NF-kB and PI3K inhibition by L. reuteri CRL1098 soluble factors contributed to these inhibitory effects. Inhibition of PI3K/Akt pathway and the diminished expression of CD14 could be involved in the immunoregulatory effect. In addition, our in vivo data proved that the LPS-induced secretion of the pro-inflammatory cytokines, inflammatory cells recruitment to the airways and inflammatory lung tissue damage were reduced in L. reuteri CRL1098 soluble factors treated mice, providing a new way to reduce excessive pulmonary inflammation.

Host cytokine responses distinguish invasive from airway isolates of the Streptococcus milleri/anginosis group

Background

The Streptococcus Milleri/Anginosus Group (SMG) colonize mucosal surfaces, especially the airways, and are considered to be normal mucosal microbiota; however, they are a major cause of abscesses, pneumonia and pleural empyema. The production of exoenzymes and virulence factors do not correlate with SMG pathogenicity. Since SMG infections are associated with robust inflammatory responses, we hypothesized that host immune responses might distinguish strains associated with asymptomatic carriage and those associated with fulminant disease.

Methods

We measured IL1β, TNF, IL10, IL12, IL23, IL17, and IL4 production from human peripheral blood mononuclear cells (PBMCs) stimulated with a panel of clinical isolates from the airways and infections and measured the ability of these isolates to stimulate TLR2.

Results

Isolates were categorized based on the levels of cytokines they induced from PBMCs (high, intermediate, low). Airway isolates predominantly induced low levels of cytokines and isolates from invasive disease induced higher levels, although about 10% of the strains produced divergent cytokine responses between donors. Interestingly, the donors were most divergent in their production of IL17, IL12 and IL23.

Conclusions

We propose that the ability to inhibit or avoid an inflammatory response is associated with carriage in the airways and variability in responses between isolates and donors might contribute to susceptibility to disease.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2334-14-498) contains supplementary material, which is available to authorized users.

Could T cells be involved in lung deterioration and hyperglycemia in cystic fibrosis?

Cystic fibrosis-related diabetes (CFRD) is the most frequent complication of cystic fibrosis (CF) and associated with increased mortality. Why patients have an accelerated loss of lung function before the diagnosis of CFRD remains poorly understood. We reported that patients with or without CFRD had increased glucose excursions when compared to healthy peers. Studies have demonstrated that patients with CF have increased glucose fluctuations and hyperglycemia and that this may affect the clinical course of CF and lead to lymphocyte dysfunction. T-helper 17 (Th17) lymphocytes produce and secrete the pro-inflammatory cytokine IL-17. The Th17 pathway is involved in CF lung inflammation, β-cell destruction in type 1 diabetes (T1D) and Th17 cells of patients with type 2 diabetes have increased production of IL-17 when compared to healthy peers. Also, regulatory T-cells (Tregs) have been shown to be dysfunctional and produce IL-17 in T1D. Furthermore, vitamin D can affect inflammation in CF, diabetes and the differentiation of lymphocytes. In this review, we discuss the potential roles of hyperglycemia on Th17 cells, Tregs and IL-17 as a potential cause for accelerated lung function decline before CFRD and how this could be modulated by vitamin D or by directly intervening in the IL-17A pathway.

Functional roles of p38 mitogen-activated protein kinase in macrophage-mediated inflammatory responses

Inflammation is a natural host defensive process that is largely regulated by macrophages during the innate immune response. Mitogen-activated protein kinases (MAPKs) are proline-directed serine and threonine protein kinases that regulate many physiological and pathophysiological cell responses. p38 MAPKs are key MAPKs involved in the production of inflammatory mediators, including tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2). p38 MAPK signaling plays an essential role in regulating cellular processes, especially inflammation. In this paper, we summarize the characteristics of p38 signaling in macrophage-mediated inflammation. In addition, we discuss the potential of using inhibitors targeting p38 expression in macrophages to treat inflammatory diseases.