Early life microbiome perturbation alters pulmonary responses to ozone in male mice

Thymic stromal lymphopoietin contributes to ozone-induced exacerbations of eosinophilic airway inflammation via granulocyte colony-stimulating factor in mice

BACKGROUND

Ozone is one of the triggers of asthma, but its impact on the pathophysiology of asthma, such as via airway inflammation and airway hyperresponsiveness (AHR), is not fully understood. Thymic stromal lymphopoietin (TSLP) is increasingly seen as a crucial molecule associated with asthma severity, such as corticosteroid resistance.

METHODS

Female BALB/c mice sensitized and challenged with house dust mite (HDM) were exposed to ozone at 2 ppm for 3 h. Airway inflammation was assessed by the presence of inflammatory cells in bronchoalveolar lavage fluid and concentrations of cytokines including TSLP in lung. Anti-TSLP antibody was administered to mice to block the signal. Survival and adhesion of bone marrow-derived eosinophils in response to granulocyte colony-stimulating factor (G-CSF) were evaluated.

RESULTS

Ozone exposure increased eosinophilic airway inflammation and AHR in mice sensitized and challenged with HDM. In addition, TSLP, but not IL-33 and IL-25, was increased in lung by ozone exposure. To confirm whether TSLP signaling is associated with airway responses to ozone, an anti-TSLP antibody was administered, and it significantly attenuated eosinophilic airway inflammation, but not AHR. Interestingly, G-CSF, but not type 2 cytokines such as IL-4, IL-5, and IL-13, was regulated by TSLP signaling associated with eosinophilic airway inflammation, and G-CSF prolonged survival and activated eosinophil adhesion.

CONCLUSIONS

The present data show that TSLP contributes to ozone-induced exacerbations of eosinophilic airway inflammation and provide greater understanding of ozone-induced severity mechanisms in the pathophysiology of asthma related to TSLP and G-CSF.

Weanling gut microbiota composition of a mouse model selectively bred for high voluntary wheel-running behavior

We compared the fecal microbial community composition and diversity of four replicate lines of mice selectively bred for high wheel-running activity over 81 generations (HR lines) and four non-selected control lines. We performed 16S rRNA gene sequencing on fecal samples taken 24 h after weaning, identifying a total of 2074 bacterial operational taxonomic units. HR and control mice did not significantly differ for measures of alpha diversity, but HR mice had a higher relative abundance of the family Clostridiaceae. These results differ from a study of rats, where a line bred for high forced-treadmill endurance and that also ran more on wheels had lower relative abundance of Clostridiaceae, as compared with a line bred for low endurance that ran less on wheels. Within the HR and control groups, replicate lines had unique microbiomes based on unweighted UniFrac beta diversity, indicating random genetic drift and/or multiple adaptive responses to selection.

Effect of Azithromycin on Exacerbations in Asthma Patients with Obesity: Protocol for a Multi-Center, Prospective, Single-Arm Intervention Study

INTRODUCTION

Obesity is associated with severe asthma, but no specific treatment has been established. The gut microbiome is increasingly recognized as a crucial factor, but specific treatments focused on the gut microbiome have not been established. Recently, azithromycin has been found to have the capacity to attenuate exacerbations, a characteristic of severe asthma. The effect of azithromycin on obesity-induced severe asthma is not understood.

METHODS

The purpose of the present study is to clarify the effect of azithromycin on exacerbations in asthmatic patients with obesity. To explore the mechanism, the gut microbiome, metabolites of microbes such as short-chain fatty acids, and blood inflammatory cytokines will be analyzed to evaluate the correlation with the effect of azithromycin on exacerbations in obesity-induced severe asthma. A multi-center, prospective, single-arm intervention study is planned.

DISCUSSION

The present study will allow us to evaluate the effect of azithromycin on exacerbations, particularly in asthma patients with obesity, and explore biomarkers, targeting molecules including the gut microbiome, which are correlated with decreased exacerbations. The present results could contribute to identifying new therapeutic prospects and targeted microbes or molecules associated with severe clinical characteristics in asthmatic patients with obesity.

TRIAL REGISTRATION

This study has been registered as a prospective study with the University Hospital Medical Information Network (UMIN0000484389) and the Japan Registry of Clinical Trials (jRCTs071220023).

Change of intestinal microbiota in mice model of bronchopulmonary dysplasia

Background

Gut microbiota has been proposed to be related to the pathogenesis of pulmonary diseases such as asthma and lung cancer, according to the gut-lung axis. However, little is known about the roles of gut microbiota in the pathogenesis of bronchopulmonary dysplasia (BPD). This study was designed to investigate the changes of gut microbiota in neonatal mice with BPD.

Methods

BPD model was induced through exposure to high concentration of oxygen. Hematoxylin and eosin (H&E) staining was utilized to determine the modeling efficiency. Stool samples were collected from the distal colon for the sequencing of V3-V4 regions of 16S rRNA, in order to analyze the gut microbiota diversity.

Results

Alpha diversity indicated that there were no statistical differences in the richness of gut microbiota between BPD model group and control group on day 7, 14 and 21. Beta diversity analysis showed that there were statistical differences in the gut microbiota on day 14 (R = 0.368, p = 0.021). Linear discriminant analysis effect size (LEfSe) showed that there were 22 markers with statistical differences on day 14 (p < 0.05), while those on day 7 and 21 were 3 and 4, respectively. Functional prediction analysis showed that the top three metabolic pathways were signal transduction (P_FDR = 0.037), glycan biosynthesis and metabolism (P_FDR = 0.032), and metabolism of terpenoids and polyketides (P_FDR = 0.049).

Conclusions

BPD mice showed disorder of gut microbiota, which may involve specific metabolic pathways in the early stage. With the progression of neonatal maturity, the differences of the gut microbiota between the two groups would gradually disappear.

Does the gut microbiome partially mediate the impact of air pollutants exposure on liver function? Evidence based on schizophrenia patients

Air pollution may alter the composition of gut microbiome and subsequent liver-related metabolic disorders. Schizophrenia was often accompanied by liver dysfunction. But it was still unclear whether air pollutants affected liver function in patients with schizophrenia through gut microbiome. We aimed to clarify the impacts of long-term air pollutants on the gut microbiome and liver function in schizophrenia and to evaluate the intermediary effect of microbiome. Schizophrenia patients were recruited then serum biochemical indicators were tested. Air pollutant exposure in the previous year was retrospectively estimated by inverse distance weighting. The associations among air pollutants, gut microbiome, and liver function indicators in schizophrenia were estimated. Then the mediating effect of gut microbiome was further explored. The results showed that nitrogen dioxide (NO₂), carbonic oxide (CO), ozone (O₃), particulate matter with aerodynamic diameter ≤10 μm (PM₁₀), and fine particulate matter (PM_2.5) explained 2.68%-10.77% of the variation in gut microbiome composition (order level) in schizophrenia (all P < 0.05). Network correlation analysis indicated that air pollutants and liver function indicators were mainly related to Firmicutes, Actinobacteria, and Proteobacteria in schizophrenia. Long-term NO₂ exposure significantly increased the levels of gamma-glutamyl transpeptidase (GGT) and glutamic pyruvic transaminase (GPT) in schizophrenia. Coriobacteriales mediated 13.98% and 49.56% (all P < 0.05) of the associations of long-term NO₂ with GGT and GPT, respectively. To conclude, long-term NO₂ exposure is positively associated with liver dysfunction in schizophrenia, in which gut microbiome plays an intermediary role. The two pathways, "NO₂-Coriobacteriales-GGT" and "NO₂-Coriobacteriales-GPT", would provide scientific evidence for the intervention of schizophrenia with liver dysfunction.

Taxonomic composition and variation in the gut microbiota of laboratory mice

The gut microbiota can affect host health, including humans. Mouse models have been used extensively to study the relationships between the host and the gut microbiota. With the development of cost-effective high-throughput DNA sequencing, several methods have been used to identify members of the gut microbiota of laboratory mice. In recent years, the amount of research and knowledge about the mouse gut microbiota has exploded, leading to significant breakthroughs in understanding of the taxonomic composition of and variation in this community. In addition, the rapidly increasing volume of data has allowed the development of public resources for exploring the mouse gut microbiota. In this review, we describe the concepts and pros and cons of basic methodologies that can be used to determine the gut bacterial profile in laboratory mice. We also present the key bacterial components of the mouse gut microbiota from the phylum to the species level and then compare them with those identified in other references. Additionally, we discuss variations in the mouse gut microbiota and their association with experiments using mice. Finally, we summarize the properties and functions of currently available public resources for exploring the mouse gut microbiota.

The Gut Microbiome and Ozone-induced Airway Hyperresponsiveness. Mechanisms and Therapeutic Prospects

In recent years, several new asthma therapeutics have been developed. Although many of these agents show promise in treating allergic asthma, they are less effective against nonallergic forms of asthma. The gut microbiome has important roles in human health and disease, and a growing body of evidence indicates a link between the gut microbiome and asthma. Here, we review those data focusing on the role of the microbiome in mouse models of nonallergic asthma including obese asthma and asthma triggered by exposure to air pollutants. We describe the impact of antibiotics, diet, and early life events on airway responses to the air pollutant ozone, including in the setting of obesity. We also review potential mechanisms responsible for gut-lung interactions focusing on bacterial-derived metabolites, the immune system, and hormones. Finally, we discuss future prospects for gut microbiome-targeted therapies such as fecal microbiome transplantation, prebiotics, probiotics, and prudent use of antibiotics. Better understanding of the role of the microbiome in airway responses may lead to exploration of new microbiome-targeted therapies to control asthma, especially nonallergic forms of asthma.

Early-life effects of juvenile Western diet and exercise on adult gut microbiome composition in mice

Alterations to the gut microbiome caused by changes in diet, consumption of antibiotics, etc., can affect host function. Moreover, perturbation of the microbiome during critical developmental periods potentially has long-lasting impacts on hosts. Using four selectively bred high runner and four non-selected control lines of mice, we examined the effects of early-life diet and exercise manipulations on the adult microbiome by sequencing the hypervariable internal transcribed spacer region of the bacterial gut community. Mice from high runner lines run ∼3-fold more on wheels than do controls, and have several other phenotypic differences (e.g. higher food consumption and body temperature) that could alter the microbiome, either acutely or in terms of coevolution. Males from generation 76 were given wheels and/or a Western diet from weaning until sexual maturity at 6 weeks of age, then housed individually without wheels on standard diet until 14 weeks of age, when fecal samples were taken. Juvenile Western diet reduced bacterial richness and diversity after the 8-week washout period (equivalent to ∼6 human years). We also found interactive effects of genetic line type, juvenile diet and/or juvenile exercise on microbiome composition and diversity. Microbial community structure clustered significantly in relation to both line type and diet. Western diet also reduced the relative abundance of Muribaculum intestinale These results constitute one of the first reports of juvenile diet having long-lasting effects on the adult microbiome after a substantial washout period. Moreover, we found interactive effects of diet with early-life exercise exposure, and a dependence of these effects on genetic background.

Gut microbiota from androgen-altered donors alter pulmonary responses to ozone in female mice

In mice, both androgens and the gut microbiota modify pulmonary responses to ozone. We hypothesized that androgens affect gut microbiota and thereby impact pulmonary responses to ozone. To address this hypothesis, we transferred cecal microbiota from male castrated or sham castrated C57BL/6J mice into female germ-free recipient C57BL/6J mice. Four weeks later mice were exposed to ozone (2 ppm) or room air for 3 hr. The gut microbiomes of castrated versus sham castrated donors differed, as did those of recipients of microbiota from castrated versus sham castrated donors. In recipients, ozone-induced airway hyperresponsiveness was not affected by donor castration status. However, compared to mice receiving microbiota from sham castrated donors, mice receiving microbiota from castrated donors had elevated numbers of bronchoalveolar lavage (BAL) neutrophils despite evidence of reduced lung injury as measured by BAL protein. Serum concentrations of IL-17A and G-CSF were significantly greater in recipients of castrated versus sham castrated microbiota. Furthermore, BAL neutrophils correlated with both serum IL-17A and serum G-CSF. Our data indicate that androgen-mediated effects on the gut microbiota modulate pulmonary inflammatory responses to ozone and suggest a role for circulating IL-17A and G-CSF in these events.

Microbiota-immune interactions in asthma pathogenesis and phenotype

The complexity and the mechanistic role of microbial communities at mucosal surfaces are only now beginning to be understood. Their impact on host metabolism, development, and immune responses to infectious and inert stimuli may be centrally linked to the metabolic functions of these communities within the established microbiome. The structure and function of microbial communities are influenced both early and throughout life by many environmental factors, exposures, diet, and disease. Understanding how the microbiome influences the host during health is likely just as important as understanding how it influences asthmatic disease predisposition and severity.

Early life microbiome perturbation alters pulmonary responses to ozone in male mice

Early life changes in the microbiome contribute to the development of allergic asthma, but little is known about the importance of the microbiome for other forms of asthma. Ozone is a nonatopic asthma trigger that causes airway hyperresponsiveness and neutrophil recruitment to the lungs. The purpose of this study was to test the hypothesis that early life perturbations in the gut microbiome influence subsequent responses to ozone. To that end, we placed weanling mouse pups from The Jackson Laboratories or from Taconic Farms in sex-specific cages either with other mice from the same vendor (same-housed) or with mice from the opposite vendor (cohoused). Mice were maintained with these cagemates until use. The gut microbial community differs in mice from Jackson Labs and Taconic Farms, and cohousing mice transfers fecal microbiota from one mouse to another. Indeed, 16S rRNA sequencing of fecal DNA indicated that differences in the gut microbiomes of Jackson and Taconic same-housed mice were largely abolished when the mice were cohoused. At 10-12 weeks of age, mice were exposed to room air or ozone (2 ppm for 3 hr). Compared to same-housed mice, cohoused male but not female mice had reduced ozone-induced airway hyperresponsiveness and reduced ozone-induced increases in bronchoalveolar lavage neutrophils. Ozone-induced airway hyperresponsiveness was greater in male than in female mice and the sex difference was largely abolished in cohoused mice. The data indicate a role for early life microbial perturbations in pulmonary responses to a nonallergic asthma trigger.