Faecal microbial transfer and complex carbohydrates mediate protection against COPD.

OBJECTIVE: Chronic obstructive pulmonary disease (COPD) is a major cause of global illness and death, most commonly caused by cigarette smoke. The mechanisms of pathogenesis remain poorly understood, limiting the development of effective therapies. The gastrointestinal microbiome has been implicated in chronic lung diseases via the gut-lung axis, but its role is unclear. DESIGN: Using an in vivo mouse model of cigarette smoke (CS)-induced COPD and faecal microbial transfer (FMT), we characterised the faecal microbiota using metagenomics, proteomics and metabolomics. Findings were correlated with airway and systemic inflammation, lung and gut histopathology and lung function. Complex carbohydrates were assessed in mice using a high resistant starch diet, and in 16 patients with COPD using a randomised, double-blind, placebo-controlled pilot study of inulin supplementation. RESULTS: FMT alleviated hallmark features of COPD (inflammation, alveolar destruction, impaired lung function), gastrointestinal pathology and systemic immune changes. Protective effects were additive to smoking cessation, and transfer of CS-associated microbiota after antibiotic-induced microbiome depletion was sufficient to increase lung inflammation while suppressing colonic immunity in the absence of CS exposure. Disease features correlated with the relative abundance of Muribaculaceae, Desulfovibrionaceae and Lachnospiraceae family members. Proteomics and metabolomics identified downregulation of glucose and starch metabolism in CS-associated microbiota, and supplementation of mice or human patients with complex carbohydrates improved disease outcomes. CONCLUSION: The gut microbiome contributes to COPD pathogenesis and can be targeted therapeutically.

Antiviral Responses of Tissue-resident CD49a+ Lung Natural Killer Cells Are Dysregulated in Chronic Obstructive Pulmonary Disease.

Rationale: Tissue-resident natural killer (trNK) cells have been identified in numerous organs, but little is known about their functional contribution to respiratory immunity, in particular during chronic lung diseases such as chronic obstructive pulmonary disease (COPD). Objectives: To investigate the phenotype and antiviral responses of trNK cells in murine cigarette smoke-induced experimental COPD and in human lung parenchyma from COPD donors. Methods: Mice were exposed to cigarette smoke for 12 weeks to induce COPD-like lung disease. Lung trNK cell phenotypes and function were analyzed by flow cytometry in both murine and human disease with and without challenge with influenza A virus. Measurements and Main Results: In the mouse lung, CD49a+CD49b+EOMES+ and CD49a+CD49b-EOMESlo NK cell populations had a distinct phenotype compared with CD49a- circulating NK cells. CD49a+ NK cells were more extensively altered earlier in disease onset than circulating NK cells, and increased proportions of CD49a+ NK cells correlated with worsening disease in both murine and human COPD. Furthermore, the presence of lung disease delayed both circulating and trNK cell functional responses to influenza infection. CD49a+ NK cells markedly increased their NKG2D, CD103, and CD69 expression in experimental COPD after influenza infection, and human CD49a+ NK cells were hyperactive to ex vivo influenza infection in COPD donors. Conclusions: Collectively, these results demonstrate that trNK cell function is altered in cigarette smoke-induced disease and suggests that smoke exposure may aberrantly prime trNK cell responsiveness to viral infection. This may contribute to excess inflammation during viral exacerbations of COPD.

Airway and parenchymal transcriptomics in a novel model of asthma and COPD overlap.

BACKGROUND: Asthma and chronic obstructive pulmonary disease (COPD) are common chronic respiratory diseases, and some patients have overlapping disease features, termed asthma-COPD overlap (ACO). Patients characterized with ACO have increased disease severity; however, the mechanisms driving this have not been widely studied. OBJECTIVES: This study sought to characterize the phenotypic and transcriptomic features of experimental ACO in mice induced by chronic house dust mite antigen and cigarette smoke exposure. METHODS: Female BALB/c mice were chronically exposed to house dust mite antigen for 11 weeks to induce experimental asthma, cigarette smoke for 8 weeks to induce experimental COPD, or both concurrently to induce experimental ACO. Lung inflammation, structural changes, and lung function were assessed. RNA-sequencing was performed on separated airway and parenchyma lung tissues to assess transcriptional changes. Validation of a novel upstream driver SPI1 in experimental ACO was assessed using the pharmacological SPI1 inhibitor, DB2313. RESULTS: Experimental ACO recapitulated features of both asthma and COPD, with mixed pulmonary eosinophilic/neutrophilic inflammation, small airway collagen deposition, and increased airway hyperresponsiveness. Transcriptomic analysis identified common and distinct dysregulated gene clusters in airway and parenchyma samples in experimental asthma, COPD, and ACO. Upstream driver analysis revealed increased expression of the transcription factor Spi1. Pharmacological inhibition of SPI1 using DB2313, reduced airway remodeling and airway hyperresponsiveness in experimental ACO. CONCLUSIONS: A new experimental model of ACO featuring chronic dual exposures to house dust mite and cigarette smoke mimics key disease features observed in patients with ACO and revealed novel disease mechanisms, including upregulation of SPI1, that are amenable to therapy.

Aim2 suppresses cigarette smoke-induced neutrophil recruitment, neutrophil caspase-1 activation and anti-Ly6G-mediated neutrophil depletion.

Increased inflammasome responses are strongly implicated in inflammatory diseases; however, their specific roles are incompletely understood. Therefore, we sought to examine the roles of nucleotide-binding oligomerization domain-like receptor (NLR) family, pyrin domain-containing 3 (NLRP3) and absent in melanoma-2 (AIM2) inflammasomes in cigarette smoke-induced inflammation in a model of experimental chronic obstructive pulmonary disease (COPD). We targeted NLRP3 with the inhibitor MCC950 given prophylactically or therapeutically and examined Aim2-/- mice in cigarette smoke-induced experimental COPD. MCC950 treatment had minimal effects on disease development and/or progression. Aim2-/- mice had increased airway neutrophils with decreased caspase-1 levels, independent of changes in lung neutrophil chemokines. Suppressing neutrophils with anti-Ly6G in experimental COPD in wild-type mice reduced neutrophils in bone marrow, blood and lung. By contrast, anti-Ly6G treatment in Aim2-/- mice with experimental COPD had no effect on neutrophils in bone marrow, partially reduced neutrophils in the blood and had no effect on neutrophils or neutrophil caspase-1 levels in the lungs. These findings identify that following cigarette smoke exposure, Aim2 is important for anti-Ly6G-mediated depletion of neutrophils, suppression of neutrophil recruitment and mediates activation of caspase-1 in neutrophils.

Probiotic Bifidobacterium longum subsp. longum Protects against Cigarette Smoke-Induced Inflammation in Mice.

Bifidobacterium are prominent gut commensals that produce the short-chain fatty acid (SCFA) acetate, and they are often used as probiotics. Connections between the gut and the lung, termed the gut-lung axis, are regulated by the microbiome. The gut-lung axis is increasingly implicated in cigarette smoke-induced diseases, and cigarette smoke exposure has been associated with depletion of Bifidobacterium species. In this study, we assessed the impact of acetate-producing Bifidobacterium longum subsp. longum (WT) and a mutant strain with an impaired acetate production capacity (MUT) on cigarette smoke-induced inflammation. The mice were treated with WT or MUT B. longum subsp. longum and exposed to cigarette smoke for 8 weeks before assessments of lung inflammation, lung tissue gene expression and cecal SCFAs were performed. Both strains of B. longum subsp. longum reduced lung inflammation, inflammatory cytokine expression and adhesion factor expression and alleviated cigarette smoke-induced depletion in caecum butyrate. Thus, the probiotic administration of B. longum subsp. longum, irrespective of its acetate-producing capacity, alleviated cigarette smoke-induced inflammation and the depletion of cecal butyrate levels.

Impact of diet and the bacterial microbiome on the mucous barrier and immune disorders.

The prevalence of chronic immune and metabolic disorders is increasing rapidly. In particular, inflammatory bowel diseases, obesity, diabetes, asthma and chronic obstructive pulmonary disease have become major healthcare and economic burdens worldwide. Recent advances in microbiome research have led to significant discoveries of associative links between alterations in the microbiome and health, as well as these chronic supposedly noncommunicable, immune/metabolic disorders. Importantly, the interplay between diet, microbiome and the mucous barrier in these diseases has gained significant attention. Diet modulates the mucous barrier via alterations in gut microbiota, resulting in either disease onset/exacerbation due to a "poor" diet or protection against disease with a "healthy" diet. In addition, many mucosa-associated disorders possess a specific gut microbiome fingerprint associated with the composition of the mucous barrier, which is further influenced by host-microbiome and inter-microbial interactions, dietary choices, microbe immigration and antimicrobials. Our review focuses on the interactions of diet (macronutrients and micronutrients), gut microbiota and mucous barriers (gastrointestinal and respiratory tract) and their importance in the onset and/or progression of major immune/metabolic disorders. We also highlight the key mechanisms that could be targeted therapeutically to prevent and/or treat these disorders.

Microbiomes in respiratory health and disease: An Asia-Pacific perspective.

There is currently enormous interest in studying the role of the microbiome in health and disease. Microbiome's role is increasingly being applied to respiratory diseases, in particular COPD, asthma, cystic fibrosis and bronchiectasis. The changes in respiratory microbiomes that occur in these diseases and how they are modified by environmental challenges such as cigarette smoke, air pollution and infection are being elucidated. There is also emerging evidence that gut microbiomes play a role in lung diseases through the modulation of systemic immune responses and can be modified by diet and antibiotic treatment. There are issues that are particular to the Asia-Pacific region involving diet and prevalence of specific respiratory diseases. Each of these issues is further complicated by the effects of ageing. The challenges now are to elucidate the cause and effect relationships between changes in microbiomes and respiratory diseases and how to translate these into new treatments and clinical care. Here we review the current understanding and progression in these areas.

The role of acute and chronic respiratory colonization and infections in the pathogenesis of COPD.

COPD is a major global concern, increasingly so in the context of ageing populations. The role of infections in disease pathogenesis and progression is known to be important, yet the mechanisms involved remain to be fully elucidated. While COPD pathogens such as Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae are strongly associated with acute exacerbations of COPD (AECOPD), the clinical relevance of these pathogens in stable COPD patients remains unclear. Immune responses in stable and colonized COPD patients are comparable to those detected in AECOPD, supporting a role for chronic colonization in COPD pathogenesis through perpetuation of deleterious immune responses. Advances in molecular diagnostics and metagenomics now allow the assessment of microbe-COPD interactions with unprecedented personalization and precision, revealing changes in microbiota associated with the COPD disease state. As microbial changes associated with AECOPD, disease severity and therapeutic intervention become apparent, a renewed focus has been placed on the microbiology of COPD and the characterization of the lung microbiome in both its acute and chronic states. Characterization of bacterial, viral and fungal microbiota as part of the lung microbiome has the potential to reveal previously unrecognized prognostic markers of COPD that predict disease outcome or infection susceptibility. Addressing such knowledge gaps will ultimately lead to a more complete understanding of the microbe-host interplay in COPD. This will permit clearer distinctions between acute and chronic infections and more granular patient stratification that will enable better management of these features and of COPD.

Comparison of commercially available differentiation media on cell morphology, function, and anti-viral responses in conditionally reprogrammed human bronchial epithelial cells.

Primary air liquid interface (ALI) cultures of bronchial epithelial cells are used extensively to model airway responses. A recent advance is the development of conditional reprogramming that enhances proliferative capability. Several different media and protocols are utilized, yet even subtle differences may influence cellular responses. We compared the morphology and functional responses, including innate immune responses to rhinovirus infection in conditionally reprogrammed primary bronchial epithelial cells (pBECs) differentiated using two commonly used culture media. pBECs collected from healthy donors (n = 5) were CR using g-irradiated 3T3 fibroblasts and Rho Kinase inhibitor. CRpBECs were differentiated at ALI in either PneumaCult (PN-ALI) or bronchial epithelial growth medium (BEGM)-based differentiation media (BEBM:DMEM, 50:50, Lonza)-(AB-ALI) for 28 days. Transepithelial electrical resistance (TEER), immunofluorescence, histology, cilia activity, ion channel function, and expression of cell markers were analyzed. Viral RNA was assessed by RT-qPCR and anti-viral proteins quantified by LEGENDplex following Rhinovirus-A1b infection. CRpBECs differentiated in PneumaCult were smaller and had a lower TEER and cilia beat frequency compared to BEGM media. PneumaCult media cultures exhibited increased FOXJ1 expression, more ciliated cells with a larger active area, increased intracellular mucins, and increased calcium-activated chloride channel current. However, there were no significant changes in viral RNA or host antiviral responses. There are distinct structural and functional differences in pBECs cultured in the two commonly used ALI differentiation media. Such factors need to be taken into consideration when designing CRpBECs ALI experiments for specific research questions.

Emerging therapeutic targets and preclinical models for severe asthma.

INTRODUCTION: Asthma is a heterogeneous disease with complex multifactorial causes. It is possible to subclassify asthma into different phenotypes that have distinct immunological features. Eosinophilic asthma is a well-known phenotype of severe asthma; however, a large body of clinical and experimental evidence strongly associates persistent airway inflammation, including the accumulation of neutrophils in the bronchial mucosa, and resistance to corticosteroid therapy and non-Type-2 immune responses with severe asthma. Importantly, mainstay therapies are often ineffective in severe asthma and effective alternatives are urgently needed. AREAS COVERED: Here, we discussed recently developed mouse models of severe asthma that recapitulates key features of the disease in humans. We also provide findings from clinically relevant experimental models that have identified potential therapeutic targets for severe asthma. The most relevant publications on the topic of interest were selected from PubMed. EXPERT COMMENTARY: Increasing the understanding of disease-causing mechanisms in severe asthma may lead to the identification of novel therapeutic targets and the development of more effective therapies. Intense research interest into investigating the pathophysiological mechanisms of severe asthma has driven the development and interrogation of a myriad of mouse models that aim to replicate hallmark features of severe asthma in humans.

The role of the microbiome and the NLRP3 inflammasome in the gut and lung.

The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family, pyrin domain-containing protein 3 (NLRP3) inflammasome, is one of the most well-characterized inflammasomes, activated by pathogen-associated molecular patterns and damage-associated molecular patterns, including from commensal or pathogenic bacterial and viral infections. The NLRP3 inflammasome promotes inflammatory cell recruitment and regulates immune responses in tissues such as the gastrointestinal tract and the lung, and is involved in many diseases that affect the gut and lung. Recently, the microbiome in the gut and the lung, and the crosstalk between these organs (gut-lung axis), has been identified as a potential mechanism that may influence disease in a bidirectional manner. In this review, we focus on themes presented in this area at the 2019 World Congress on Inflammation. We discuss recent evidence on how the microbiome can affect NLRP3 inflammasome responses in the gut and lung, the role of this inflammasome in regulating gut and lung inflammation in disease, and its potential role in the gut-lung axis. We highlight the exponential increase in our understanding of the NLRP3 inflammasome due to the synthesis of the NLRP3 inflammasome inhibitor, MCC950, and propose future studies that may further elucidate the roles of the NLRP3 inflammasome in gut and lung diseases.

Disease-associated gut microbiome and metabolome changes in patients with chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is the third commonest cause of death globally, and manifests as a progressive inflammatory lung disease with no curative treatment. The lung microbiome contributes to COPD progression, but the function of the gut microbiome remains unclear. Here we examine the faecal microbiome and metabolome of COPD patients and healthy controls, finding 146 bacterial species differing between the two groups. Several species, including Streptococcus sp000187445, Streptococcus vestibularis and multiple members of the family Lachnospiraceae, also correlate with reduced lung function. Untargeted metabolomics identifies a COPD signature comprising 46% lipid, 20% xenobiotic and 20% amino acid related metabolites. Furthermore, we describe a disease-associated network connecting Streptococcus parasanguinis_B with COPD-associated metabolites, including N-acetylglutamate and its analogue N-carbamoylglutamate. While correlative, our results suggest that the faecal microbiome and metabolome of COPD patients are distinct from those of healthy individuals, and may thus aid in the search for biomarkers for COPD.

Role of Lung Microbiome in Innate Immune Response Associated With Chronic Lung Diseases.

Respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), lung fibrosis, and lung cancer, pose a huge socio-economic burden on society and are one of the leading causes of death worldwide. In the past, culture-dependent techniques could not detect bacteria in the lungs, therefore the lungs were considered a sterile environment. However, the development of culture-independent techniques, particularly 16S rRNA sequencing, allowed for the detection of commensal microbes in the lung and with further investigation, their roles in disease have since emerged. In healthy individuals, the predominant commensal microbes are of phylum Firmicutes and Bacteroidetes, including those of the genera Veillonella and Prevotella. In contrast, pathogenic microbes (Haemophilus, Streptococcus, Klebsiella, Pseudomonas) are often associated with lung diseases. There is growing evidence that microbial metabolites, structural components, and toxins from pathogenic and opportunistic bacteria have the capacity to stimulate both innate and adaptive immune responses, and therefore can contribute to the pathogenesis of lung diseases. Here we review the multiple mechanisms that are altered by pathogenic microbiomes in asthma, COPD, lung cancer, and lung fibrosis. Furthermore, we focus on the recent exciting advancements in therapies that can be used to restore altered microbiomes in the lungs.

Functional effects of the microbiota in chronic respiratory disease.

The composition of the lung microbiome is increasingly well characterised, with changes in microbial diversity or abundance observed in association with several chronic respiratory diseases such as asthma, cystic fibrosis, bronchiectasis, and chronic obstructive pulmonary disease. However, the precise effects of the microbiome on pulmonary health and the functional mechanisms by which it regulates host immunity are only now beginning to be elucidated. Bacteria, viruses, and fungi from both the upper and lower respiratory tract produce structural ligands and metabolites that interact with the host and alter the development and progression of chronic respiratory diseases. Here, we review recent advances in our understanding of the composition of the lung microbiome, including the virome and mycobiome, the mechanisms by which these microbes interact with host immunity, and their functional effects on the pathogenesis, exacerbations, and comorbidities of chronic respiratory diseases. We also describe the present understanding of how respiratory microbiota can influence the efficacy of common therapies for chronic respiratory disease, and the potential of manipulation of the microbiome as a therapeutic strategy. Finally, we highlight some of the limitations in the field and propose how these could be addressed in future research.

Microbiome-focused asthma management strategies.

Asthma is a common, heterogeneous and serious disease with high prevalence globally. Poorly controlled, steroid-resistant asthma is particularly important as there are no effective therapies and it exerts substantial healthcare and societal burden. The role of microbiomes, particularly in chronic diseases has generated considerable interest in recent times. Existing evidence clearly demonstrates an association between asthma initiation and the microbiome, both respiratory and gastro-intestinal, although its' roles are poorly understood when assessing the asthma progression or heterogeneity (i.e. phenotypes/endotypes) across different geographical locations. Moreover, modulating microbiomes could be preventive and/or therapeutic in patients with asthma warrants urgent attention. Here, we review recent advances in assessing the role of microbiomes in asthma and present the challenges associated with the potential therapeutic utility of modifying microbiomes in management.

Microbiome effects on immunity, health and disease in the lung.

Chronic respiratory diseases, including asthma, chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF), are among the leading causes of mortality and morbidity worldwide. In the past decade, the interest in the role of microbiome in maintaining lung health and in respiratory diseases has grown exponentially. The advent of sophisticated multiomics techniques has enabled the identification and characterisation of microbiota and their roles in respiratory health and disease. Furthermore, associations between the microbiome of the lung and gut, as well as the immune cells and mediators that may link these two mucosal sites, appear to be important in the pathogenesis of lung conditions. Here we review the recent evidence of the role of normal gastrointestinal and respiratory microbiome in health and how dysbiosis affects chronic pulmonary diseases. The potential implications of host and environmental factors such as age, gender, diet and use of antibiotics on the composition and overall functionality of microbiome are also discussed. We summarise how microbiota may mediate the dynamic process of immune development and/or regulation focusing on recent data from both clinical human studies and translational animal studies. This furthers the understanding of the pathogenesis of chronic pulmonary diseases and may yield novel avenues for the utilisation of microbiota as potential therapeutic interventions.

Emerging pathogenic links between microbiota and the gut-lung axis.

The microbiota is vital for the development of the immune system and homeostasis. Changes in microbial composition and function, termed dysbiosis, in the respiratory tract and the gut have recently been linked to alterations in immune responses and to disease development in the lungs. In this Opinion article, we review the microbial species that are usually found in healthy gastrointestinal and respiratory tracts, their dysbiosis in disease and interactions with the gut-lung axis. Although the gut-lung axis is only beginning to be understood, emerging evidence indicates that there is potential for manipulation of the gut microbiota in the treatment of lung diseases.