Butyrate Attenuates Lung Inflammation by Negatively Modulating Th9 Cells

Assessment of progression of pulmonary fibrosis based on metabonomics and analysis of intestinal microbiota

The main purpose of this study was to explore the changes of biomarkers in different developmental stages of bleomycin-induced pulmonary fibrosis (PF) in rats via comprehensive pathophysiology, UPLC-QTOF/MS metabonomic technology, and 16S rRNA gene sequencing of intestinal microbiota. The rats were randomly divided into normal control and 1-, 2- and 4-week model group. The rat model of PF was established by one-time intratracheal instillation of bleomycin. The levels of inflammatory and fibrosis-related factors such as hydroxyproline (HYP), type III procollagen (COL-III), type IV collagen (COL-IV), hyaluronidase (HA), laminin (LN), interleukin (IL)-1β, IL-6, malondialdehyde (MDA) increased and superoxide dismutase (SOD) decreased as the PF cycle progressed. In the 1-, 2- and 4-week model group, 2, 19 and 18 potential metabolic biomarkers and 3, 16 and 12 potential microbial biomarkers were detected, respectively, which were significantly correlated. Glycerophospholipid metabolism pathway was observed to be an important pathway affecting PF at 1, 2 and 4 weeks; arginine and proline metabolism pathways significantly affected PF at 2 weeks. Linoleic acid metabolism pathway exhibited clear metabolic abnormalities at 2 and 4 weeks of PF, and alpha-linolenic acid metabolism pathway significantly affected PF at 4 weeks.

Short-Chain Fatty Acid (SCFA) as a Connecting Link between Microbiota and Gut-Lung Axis-A Potential Therapeutic Intervention to Improve Lung Health

The microbiome is an integral part of the human gut, and it plays a crucial role in the development of the immune system and homeostasis. Apart from the gut microbiome, the airway microbial community also forms a distinct and crucial part of the human microbiota. Furthermore, several studies indicate the existence of communication between the gut microbiome and their metabolites with the lung airways, called "gut-lung axis". Perturbations in gut microbiota composition, termed dysbiosis, can have acute and chronic effects on the pathophysiology of lung diseases. Microbes and their metabolites in lung stimulate various innate immune pathways, which modulate the expression of the inflammatory genes in pulmonary leukocytes. For instance, gut microbiota-derived metabolites such as short-chain fatty acids can suppress lung inflammation through the activation of G protein-coupled receptors (free fatty acid receptors) and can also inhibit histone deacetylase, which in turn influences the severity of acute and chronic respiratory diseases. Thus, modulation of the gut microbiome composition through probiotic/prebiotic usage and fecal microbiota transplantation can lead to alterations in lung homeostasis and immunity. The resulting manipulation of immune cells function through microbiota and their key metabolites paves the way for the development of novel therapeutic strategies in improving the lung health of individuals affected with various lung diseases including SARS-CoV-2. This review will shed light upon the mechanistic aspect of immune system programming through gut and lung microbiota and exploration of the relationship between gut-lung microbiome and also highlight the therapeutic potential of gut microbiota-derived metabolites in the management of respiratory diseases.

Maternal gut microbiota in the health of mothers and offspring: from the perspective of immunology

Due to the physiological alteration during pregnancy, maternal gut microbiota changes following the metabolic processes. Recent studies have revealed that maternal gut microbiota is closely associated with the immune microenvironment in utero during pregnancy and plays a vital role in specific pregnancy complications, including preeclampsia, gestational diabetes, preterm birth and recurrent miscarriages. Some other evidence has also shown that aberrant maternal gut microbiota increases the risk of various diseases in the offspring, such as allergic and neurodevelopmental disorders, through the immune alignment between mother and fetus and the possible intrauterine microbiota. Probiotics and the high-fiber diet are effective inventions to prevent mothers and fetuses from diseases. In this review, we summarize the role of maternal gut microbiota in the development of pregnancy complications and the health condition of future generations from the perspective of immunology, which may provide new therapeutic strategies for the health management of mothers and offspring.

Gut microbiota and microbiota-derived metabolites in colorectal cancer: enemy or friend

Colorectal cancer (CRC) is a highly prevalent gastrointestinal cancer worldwide. Recent research has shown that the gut microbiota plays a significant role in the development of CRC. There is mounting evidence supporting the crucial contributions of bacteria-derived toxins and metabolites to cancer-related inflammation, immune imbalances, and the response to therapy. Besides, some gut microbiota and microbiota-derived metabolites have protective effects against CRC. This review aims to summarize the current studies on the effects and mechanisms of gut microbiota and microbiota-produced metabolites in the initiation, progression, and drug sensitivity/resistance of CRC. Additionally, we explore the clinical implications and future prospects of utilizing gut microbiota as innovative approaches for preventing and treating CRC.

Regulation of short-chain fatty acids in the immune system

A growing body of research suggests that short-chain fatty acids (SCFAs), metabolites produced by intestinal symbiotic bacteria that ferment dietary fibers (DFs), play a crucial role in the health status of symbiotes. SCFAs act on a variety of cell types to regulate important biological processes, including host metabolism, intestinal function, and immune function. SCFAs also affect the function and fate of immune cells. This finding provides a new concept in immune metabolism and a better understanding of the regulatory role of SCFAs in the immune system, which impacts the prevention and treatment of disease. The mechanism by which SCFAs induce or regulate the immune response is becoming increasingly clear. This review summarizes the different mechanisms through which SCFAs act in cells. According to the latest research, the regulatory role of SCFAs in the innate immune system, including in NLRP3 inflammasomes, receptors of TLR family members, neutrophils, macrophages, natural killer cells, eosinophils, basophils and innate lymphocyte subsets, is emphasized. The regulatory role of SCFAs in the adaptive immune system, including in T-cell subsets, B cells, and plasma cells, is also highlighted. In addition, we discuss the role that SCFAs play in regulating allergic airway inflammation, colitis, and osteoporosis by influencing the immune system. These findings provide evidence for determining treatment options based on metabolic regulation.

The dynamic lung microbiome in health and disease

New methods and technologies within the field of lung biology are beginning to shed new light into the microbial world of the respiratory tract. Long considered to be a sterile environment, it is now clear that the human lungs are frequently exposed to live microbes and their by-products. The nature of the lung microbiome is quite distinct from other microbial communities inhabiting our bodies such as those in the gut. Notably, the microbiome of the lung exhibits a low biomass and is dominated by dynamic fluxes of microbial immigration and clearance, resulting in a bacterial burden and microbiome composition that is fluid in nature rather than fixed. As our understanding of the microbial ecology of the lung improves, it is becoming increasingly apparent that certain disease states can disrupt the microbial-host interface and ultimately affect disease pathogenesis. In this Review, we provide an overview of lower airway microbial dynamics in health and disease and discuss future work that is required to uncover novel therapeutic targets to improve lung health.

Gut Microbiome Composition and Its Metabolites Are a Key Regulating Factor for Malignant Transformation, Metastasis and Antitumor Immunity

The genetic and metabolomic abundance of the microbiome exemplifies that the microbiome comprises a more extensive set of genes than the entire human genome, which justifies the numerous metabolic and immunological interactions between the gut microbiota, macroorganisms and immune processes. These interactions have local and systemic impacts that can influence the pathological process of carcinogenesis. The latter can be promoted, enhanced or inhibited by the interactions between the microbiota and the host. This review aimed to present evidence that interactions between the host and the gut microbiota might be a significant exogenic factor for cancer predisposition. It is beyond doubt that the cross-talk between microbiota and the host cells in terms of epigenetic modifications can regulate gene expression patterns and influence cell fate in both beneficial and adverse directions for the host's health. Furthermore, bacterial metabolites could shift pro- and anti-tumor processes in one direction or another. However, the exact mechanisms behind these interactions are elusive and require large-scale omics studies to better understand and possibly discover new therapeutic approaches for cancer.

Targeting Lung-Gut Axis for Regulating Pollution Particle-Mediated Inflammation and Metabolic Disorders

Cigarette smoking (CS) or ambient particulate matter (PM) exposure is a risk factor for metabolic disorders, such as insulin resistance (IR), increased plasma triglycerides, hyperglycemia, and diabetes mellitus (DM); it can also cause gut microbiota dysbiosis. In smokers with metabolic disorders, CS cessation decreases the risks of serious pulmonary events, inflammation, and metabolic disorder. This review included recent studies examining the mechanisms underlying the effects of CS and PM on gut microbiota dysbiosis and metabolic disorder development; one of the potential mechanisms is the disruption of the lung-gut axis, leading to gut microbiota dysbiosis, intestinal dysfunction, systemic inflammation, and metabolic disease. Short-chain fatty acids (SCFAs) are the primary metabolites of gut bacteria, which are derived from the fermentation of dietary fibers. They activate G-protein-coupled receptor (GPCR) signaling, suppress histone deacetylase (HDAC) activity, and inhibit inflammation, facilitating the maintenance of gut health and biofunction. The aforementioned gut microbiota dysbiosis reduces SCFA levels. Treatment targeting SCFA/GPCR signaling may alleviate air pollution-associated inflammation and metabolic disorders, which involve lung-gut axis disruption.

Butyrate: More Than a Short Chain Fatty Acid

PURPOSE OF REVIEW

The mechanistic understanding of the importance and the potential benefits of the gut microbiome has exploded in potential roles in human health and disease. Short chain fatty acids (SCFAs), including butyrate, are one of the key metabolic end products that has been a major focus of microbiome understanding. This brief review aims to describe butyrate's relation to certain biological concepts and their clinical application.

RECENT FINDINGS

Butyrate has reportedly been described as a potent pro-resolution molecule that has a significant role in maintaining gut immunity, supporting gut barrier function, regulation of histone deacetylase (HDAC), and numerous systemic roles. Further research is needed to explore potential benefits of adding SCFAs for patients receiving total parenteral nutrition. Butyrate plays several biological roles in intestinal epithelium anti-inflammatory pathways with clear benefits in numerous acute and chronic disease states and overall human health helping to maintain homeostasis.

Valsartan prevents gefitinib-induced lung inflammation, oxidative stress, and alteration of plasma metabolites in rats

Gefitinib (GEF) is an inhibitor of the epidermal growth factor receptor, linked to higher risk of severe/fatal interstitial lung disease (ILD). This study was performed to determine the protective roles of an angiotensin-II type-1 receptor (AT1R) "valsartan (VAL)" in prevention of lung inflammation, oxidative stress and metabolites alteration induced by GEF. Four groups of male Wistar albino rats were received vehicle, VAL (30 mg/kg), GEF (30 mg/kg), or both for four weeks. Blood samples and lungs were harvested for plasma metabolites and histological analysis, respectively, and evaluation of inflammation and oxidative stress. GEF monotherapy showed a dense inflammation in lungs, and significantly increased tumor necrosis factor-α (P = 0.0349), interleukin-6 (P < 0.0001), chemokine ligand-3 (P = 0.0420), and interleukin-1β (P = 0.0377). GEF increased oxidative stress markers including glutathione, malondialdehyde, and catalase levels. Also, several plasma metabolites including butanoic acid, N-methylphenylethanolamine, oxalic acid, l-alanine, phosphoric acid, l-theorinine, pyroglutamic acid, and 2-bromosebacic acid were changed by GEF. The combination of VAL plus GEF reduced the inflammation and oxidative stress mediated by GEF monotherapy. In addition, the combination treatment returned plasma metabolites to the normal levels compared to GEF monotherapy. These findings revealed that VAL has a possible pulmonary protective role against pulmonary toxicity of GEF, which may lead to novel approaches for management of GEF-induced ILD.

Beyond allergic progression: From molecules to microbes as barrier modulators in the gut-lung axis functionality

The "epithelial barrier hypothesis" states that a barrier dysfunction can result in allergy development due to tolerance breakdown. This barrier alteration may come from the direct contact of epithelial and immune cells with the allergens, and indirectly, through deleterious effects caused by environmental changes triggered by industrialization, pollution, and changes in the lifestyle. Apart from their protective role, epithelial cells can respond to external factors secreting IL-25 IL-33, and TSLP, provoking the activation of ILC2 cells and a Th2-biased response. Several environmental agents that influence epithelial barrier function, such as allergenic proteases, food additives or certain xenobiotics are reviewed in this paper. In addition, dietary factors that influence the allergenic response in a positive or negative way will be also described here. Finally, we discuss how the gut microbiota, its composition, and microbe-derived metabolites, such as short-chain fatty acids, alter not only the gut but also the integrity of distant epithelial barriers, focusing this review on the gut-lung axis.

Gut-Lung Microbiota Interaction in COPD Patients: A Literature Review

Respiratory diseases are one of the leading causes of death in the world, which is why a lot of attention has been recently paid to studying the possible mechanisms for the development of pulmonary diseases and assessing the impact on their course. The microbiota plays an important role in these processes and influences the functionality of the human immune system. Thus, alterations in the normal microflora contribute to a reduction in immunity and a more severe course of diseases. In this review, we summarized the information about gut and lung microbiota interactions with particular attention to their influence on the course of chronic obstructive pulmonary disease (COPD).

Gut microbiome and human health: Exploring how the probiotic genus Lactobacillus modulate immune responses

The highest density of microbes resides in human gastrointestinal tract, known as “Gut microbiome”. Of note, the members of the genus Lactobacillus that belong to phyla Firmicutes are the most important probiotic bacteria of the gut microbiome. These gut-residing Lactobacillus species not only communicate with each other but also with the gut epithelial lining to balance the gut barrier integrity, mucosal barrier defence and ameliorate the host immune responses. The human body suffers from several inflammatory diseases affecting the gut, lungs, heart, bone or neural tissues. Mounting evidence supports the significant role of Lactobacillus spp. and their components (such as metabolites, peptidoglycans, and/or surface proteins) in modulatingimmune responses, primarily through exchange of immunological signals between gastrointestinal tract and distant organs. This bidirectional crosstalk which is mediated by Lactobacillus spp. promotes anti-inflammatory response, thereby supporting the improvement of symptoms pertaining to asthma, chronic obstructive pulmonary disease (COPD), neuroinflammatory diseases (such as multiple sclerosis, alzheimer’s disease, parkinson’s disease), cardiovascular diseases, inflammatory bowel disease (IBD) and chronic infections in patients. The metabolic disorders, obesity and diabetes are characterized by a low-grade inflammation. Genus Lactobacillus alleviates metabolic disorders by regulating the oxidative stress response and inflammatory pathways. Osteoporosis is also associated with bone inflammation and resorption. The Lactobacillus spp. and their metabolites act as powerful immune cell controllers and exhibit a regulatory role in bone resorption and formation, supporting bone health. Thus, this review demonstrated the mechanisms and summarized the evidence of the benefit of Lactobacillus spp. in alleviating inflammatory diseases pertaining to different organs from animal and clinical trials. The present narrative review explores in detail the complex interactions between the gut-dwelling Lactobacillus spp. and the immune components in distant organs to promote host’s health.

Butyrate: Connecting the gut-lung axis to the management of pulmonary disorders

Short-chain fatty acids (SCFAs) are metabolites released by bacterial components of the microbiota. These molecules have a wide range of effects in the microbiota itself, but also in host cells in which they are known for contributing to the regulation of cell metabolism, barrier function, and immunological responses. Recent studies indicate that these molecules are important players in the gut-lung axis and highlight the possibility of using strategies that alter their intestinal production to prevent or treat distinct lung inflammatory diseases. Here, we review the effects of the SCFA butyrate and its derivatives in vitro and in vivo on murine models of respiratory disorders, besides discussing the potential therapeutic use of butyrate and the other SCFAs in lung diseases.

Foxp2 inhibits Th9 cell differentiation and attenuates allergic airway inflammation in a mouse model of ovalbumin-induced asthma

This study aimed to explore the effects of forkhead box P2 gene (Foxp2) on T-helper 9 (Th9) differentiation in asthmatic mice. An in vivo asthmatic mouse model was induced with ovalbumin (OVA). An in vitro model was established by culturing CD4⁺ T cells with TGF-β, IL-4, and anti-IFN-γ. ELISA, flow cytometry, qRT-PCR and Western blot were performed to examine IL-9 secretion, Th9 cell number, and Th9 cell transcription factor expression, respectively. Pathological changes in lung tissues and airway mucus secretion were assessed with HE and PAS glycogen staining. Anti-IL-9 mAb reversed the elevation in Th9 cells and IL-9 expression in lung tissues and bronchoalveolar lavage fluid (BALF) of asthmatic mice. Foxp2 was downregulated in BALF and lung tissue of asthmatic mice and Th9 cells. Overexpression of Foxp2 inhibited Th9 cell differentiation in vitro and improved airway inflammation in vivo. Our study suggests that overexpression of Foxp2 attenuates allergic asthma by inhibiting Th9 cell differentiation.

The Effect of the Gut Microbiota on Systemic and Anti-Tumor Immunity and Response to Systemic Therapy against Cancer

Gut microbiota can have opposing functions from pro-tumorigenic to anti-tumorigenic effects. Increasing preclinical and clinical evidence suggests that the intestinal microbiota affects cancer patients’ response to immune checkpoint inhibitors (ICIs) immunotherapy, such as anti-programmed cell death protein 1 (PD-1) and its ligand (PD-L1) and anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4). Microbiota-induced inflammation possibly contributes to tumor growth and cancer development. Microbiota-derived metabolites can also be converted to carcinogenic agents related to genetic mutations and DNA damage in organs such as the colon. However, other attributes of microbiota, such as greater diversity and specific bacterial species and their metabolites, are linked to better clinical outcomes and potentially improved anti-tumor immunity. In addition, the intratumoral microbial composition strongly affects T-cell-mediated cytotoxicity and anti-tumor immune surveillance, adding more complexity to the cancer-microbiome-immune axis. Despite the emerging clinical evidence for the activity of the gut microbiota in immuno-oncology, the fundamental mechanisms of such activity are not well understood. This review provides an overview of underlying mechanisms by which the gut microbiota and its metabolites enhance or suppress anti-tumor immune responses. Understanding such mechanisms allows for better design of microbiome-specific treatment strategies to improve the clinical outcome in cancer patients undergoing systemic therapy.

Airway Administration of Bacterial Lysate OM-85 Protects Mice Against Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is a seasonal pathogen responsible for the highest percentage of viral bronchiolitis in pediatric patients. There are currently no vaccine available and therapeutic methods to mitigate the severity of RSV bronchiolitis are limited. OM-85, an oral standardized bacterial lysate isolated from human respiratory strains and widely used to prevent recurrent infections and/or exacerbations in populations at risk, has been shown to be effective and safe in children and adults. Here, we demonstrate that airway administration of OM-85 in Balb/c mice prior to infection prevents RSV-induced disease, resulting in inhibition of viral replication associated with less perivascular and peribronchial inflammation in the lungs. These protective effects are dose and time-dependent with complete protection using 1mg dose of OM-85 only four times intranasally. Mechanistic insights using this topical route in the airways revealed increased alveolar macrophages, a selective set of tolerogenic DCs, Treg and Th1 expansion in the lung, even in the absence of infection, contributing to a better Th1/Th2 balance and preventing ILC2 recruitment in the airways and associated inflammatory sequelae. OM-85 preventive treatment also improved antiviral response by increasing IFNβ and its responsive genes in the lung. In vitro, OM-85 protects against RSV infection in a type I interferon pathway. Our animal model data suggest that intranasal use of OM-85 should be considered as a potential prophylactic product to prevent RSV bronchiolitis once human studies confirm these findings.

Short-chain fatty acids-microbiota crosstalk in the coronavirus disease (COVID-19)

The novel coronavirus disease (COVID-19) still remains a major challenge to the health-care systems worldwide, inciting ongoing search for pharmaceutical and non-pharmaceutical interventions which could benefit patients already infected with SARS-CoV-2 or at increased risk thereof. Although SARS-CoV-2 primarily affects the respiratory system, it may also infect other organs and systems, including gastrointestinal tract, where it results in microbial dysbiosis. There is an emerging understanding of the role the gut microbiota plays in maintaining immune homeostasis, both inside the gastrointestinal tract and beyond (i.e. through gut-lung and gut-brain axes). One family of compounds with recognized immunomodulatory and anti-inflammatory properties are short chain fatty acids (SCFAs). SCFAs are believed that they have a protective effect in case of gastrointestinal diseases. Moreover, they are responsible for maintaining proper intestinal barrier and they take part in relevant immune functions. This review presents mechanisms of action and potential benefits of SCFA-based probiotics and direct SCFA supplementation as a strategy to support immune function amid the COVID-19 pandemic.

Dietary Fibers: Effects, Underlying Mechanisms and Possible Role in Allergic Asthma Management

The prevalence of asthma is increasing, but the cause remains under debate. Research currently focuses on environmental and dietary factors that may impact the gut-lung axis. Dietary fibers are considered to play a crucial role in supporting diversity and activity of the microbiome, as well as immune homeostasis in the gut and lung. This review discusses the current state of knowledge on how dietary fibers and their bacterial fermentation products may affect the pathophysiology of allergic asthma. Moreover, the impact of dietary fibers on early type 2 asthma management, as shown in both pre-clinical and clinical studies, is described. Short-chain fatty acids, fiber metabolites, modulate host immunity and might reduce the risk of allergic asthma development. Underlying mechanisms include G protein-coupled receptor activation and histone deacetylase inhibition. These results are supported by studies in mice, children and adults with allergic asthma. Fibers might also exert direct effects on the immune system via yet to be elucidated mechanisms. However, the effects of specific types of fiber, dosages, duration of treatment, and combination with probiotics, need to be explored. There is an urgent need to further valorize the potential of specific dietary fibers in prevention and treatment of allergic asthma by conducting more large-scale dietary intervention trials.

Immunomodulatory Role of Nutrients: How Can Pulmonary Dysfunctions Improve?

Nutrition is an important tool that can be used to modulate the immune response during infectious diseases. In addition, through diet, important substrates are acquired for the biosynthesis of regulatory molecules in the immune response, influencing the progression and treatment of chronic lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD). In this way, nutrition can promote lung health status. A range of nutrients, such as vitamins (A, C, D, and E), minerals (zinc, selenium, iron, and magnesium), flavonoids and fatty acids, play important roles in reducing the risk of pulmonary chronic diseases and viral infections. Through their antioxidant and anti-inflammatory effects, nutrients are associated with better lung function and a lower risk of complications since they can decrease the harmful effects from the immune system during the inflammatory response. In addition, bioactive compounds can even contribute to epigenetic changes, including histone deacetylase (HDAC) modifications that inhibit the transcription of proinflammatory cytokines, which can contribute to the maintenance of homeostasis in the context of infections and chronic inflammatory diseases. These nutrients also play an important role in activating immune responses against pathogens, which can help the immune system during infections. Here, we provide an updated overview of the roles played by dietary factors and how they can affect respiratory health. Therefore, we will show the anti-inflammatory role of flavonoids, fatty acids, vitamins and microbiota, important for the control of chronic inflammatory diseases and allergies, in addition to the antiviral role of vitamins, flavonoids, and minerals during pulmonary viral infections, addressing the mechanisms involved in each function. These mechanisms are interesting in the discussion of perspectives associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and its pulmonary complications since patients with severe disease have vitamins deficiency, especially vitamin D. In addition, researches with the use of flavonoids have been shown to decrease viral replication in vitro. This way, a full understanding of dietary influences can improve the lung health of patients.

IL-4 inhibits regulatory T cells differentiation by HDAC9-mediated epigenetic regulation

Regulatory T cells play a crucial role in orchestrating immune response and maintaining immune tolerance, and the expression of the Foxp3 gene is indispensable to the differentiation of regulatory T cells. IL-4 shows strong inhibitory effects on Foxp3 expression and regulatory T cells differentiation, but the detailed mechanisms are still unclear. Here, we revealed that epigenetic modulations are key to this process. Specifically, the inhibition was found to be STAT6 dependent, and HDAC9 was involved with the process of histone deacetylation at the Foxp3 locus, subsequently decreasing chromatin accessibility and Foxp3 gene transcription. Pan-histone deacetylation inhibitors, especially sodium butyrate, notably abolished the inhibitory effects of IL-4 and ameliorated allergic airway inflammation in mouse models. Our research provides important mechanistic insights into how IL-4 inhibits regulatory T cells differentiation and suggests the therapeutic potential of the sodium butyrate in allergic airway disease.

Butyrate administration strengthens the intestinal epithelium and improves intestinal dysbiosis in a cholestasis fibrosis model

AIM

Intestinal dysfunction in cirrhosis patients is linked to death by bacterial infections. Currently, there is no effective therapy for this complication. This study aims to evaluate butyrate, a novel postbiotic, on the intestinal inflammatory response, tight junction proteins and the microbiota in the cholestasis model.

METHODS AND RESULTS

Wistar rats underwent 15 days of bile duct ligation (BDL). We administered butyrate at a concentration of 1%. The BDL group did not receive treatment. The results showed that butyrate could significantly reduce pro-inflammatory cytokines (IL-17A, IFN-γ, TNF-α) in the ileum and colon while promoting IL-10 expression in the colon. Moreover, it significantly promotes tight junction protein (cld-1, occludin and ZO-1) expression in the ileum. A similar effect was observed in the colon except for ZO-1. Additionally, butyrate limited taxa diversity loss and promoted probiotic genera expansion such as Lachnospira, Prevotella and Lactobacillus. The increase in Turicibacter and Clostridiaceae distinguished the BDL group.

CONCLUSIONS

Butyrate is effective in regulating the inflammatory response, tight junction proteins and limits bacterial diversity loss.

SIGNIFICANCE AND IMPACT OF THE STUDY

This research reveals that butyrate could represent an interesting postbiotic metabolomic intervention for intestinal epithelium dysfunction in liver disease.

The microbiota-mediated dietary and nutritional interventions for COVID-19

Worldwide, scientists are looking for specific treatment for COVID-19. Apart from the antiviral approach, the interventions to support healthy immune responses to the virus are feasible through diet, nutrition, and lifestyle approaches. This narrative review explores the recent studies on dietary, nutritional, and lifestyle interventions that influence the microbiota-mediated immunomodulatory effects against viral infections. Cumulative studies reported that the airway microbiota and SARS-CoV-2 leverage each other and determine the pathogen-microbiota-host responses. Cigarette smoking can disrupt microbiota abundance. The composition and diversification of intestinal microbiota influence the airway microbiota and the innate and adaptive immunity, which require supports from the balance of macro- and micronutrients from the diet. Colorful vegetables supplied fermentable prebiotics and anti-inflammatory, antioxidant phytonutrients. Fermented foods and beverages support intestinal microbiota. In sensitive individuals, the avoidance of the high immunoreactive food antigens contributes to antiviral immunity. This review suggests associations between airway and intestinal microbiota, antiviral host immunity, and the influences of dietary, nutritional, and lifestyle interventions to prevent the clinical course toward severe COVID-19.

Coronavirus disease–2019 and the intestinal tract: An overview

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection can progress to a severe respiratory and systemic disease named coronavirus disease–2019 (COVID-19). The most common symptoms are fever and respiratory discomfort. Nevertheless, gastrointestinal infections have been reported, with symptoms such as diarrhea, nausea, vomiting, abdominal pain, and lack of appetite. Importantly, SARS-CoV-2 can remain positive in fecal samples after nasopharyngeal clearance. After gastrointestinal SARS-CoV-2 infection and other viral gastrointestinal infections, some patients may develop alterations in the gastrointestinal microbiota. In addition, some COVID-19 patients may receive antibiotics, which may also disturb gastrointestinal homeostasis. In summary, the gastrointestinal system, gut microbiome, and gut-lung axis may represent an important role in the development, severity, and treatment of COVID-19. Therefore, in this review, we explore the current pieces of evidence of COVID-19 gastrointestinal manifestations, possible implications, and interventions.

Is butyrate a natural alternative to dexamethasone in the management of CoVID-19?

Coronavirus disease 2019 (CoVID-19) caused by Severe Acute Respiratory Syndrome Coronavirus 2 has affected more than 100 million lives. Severe CoVID-19 infection may lead to acute respiratory distress syndrome and death of the patient, and is associated with hyperinflammation and cytokine storm. The broad spectrum immunosuppressant corticosteroid, dexamethasone, is being used to manage the cytokine storm and hyperinflammation in CoVID-19 patients. However, the extensive use of corticosteroids leads to serious adverse events and disruption of the gut-lung axis. Various micronutrients and probiotic supplementations are known to aid in the reduction of hyperinflammation and restoration of gut microbiota. The attenuation of the deleterious immune response and hyperinflammation could be mediated by short chain fatty acids produced by the gut microbiota. Butyric acid, the most extensively studied short chain fatty acid, is known for its anti-inflammatory properties. Additionally, butyric acid has been shown to ameliorate hyperinflammation and reduce oxidative stress in various pathologies, including respiratory viral infections. In this review, the potential anti-inflammatory effects of butyric acid that aid in cytokine storm depletion, and its usefulness in effective management of critical illness related to CoVID-19 have been discussed.

Every breath you take: Impacts of environmental dust exposure on intestinal barrier function-from the gut-lung axis to COVID-19

As countries continue to industrialize, major cities experience diminished air quality, whereas rural populations also experience poor air quality from sources such as agricultural operations. These exposures to environmental pollution from both rural and populated/industrialized sources have adverse effects on human health. Although respiratory diseases (e.g., asthma and chronic obstructive pulmonary disease) are the most commonly reported following long-term exposure to particulate matter and hazardous chemicals, gastrointestinal complications have also been associated with the increased risk of lung disease from inhalation of polluted air. The interconnectedness of these organ systems has offered valuable insights into the roles of the immune system and the micro/mycobiota as mediators of communication between the lung and the gut during disease states. A topical example of this relationship is provided by reports of multiple gastrointestinal symptoms in patients with coronavirus disease 2019 (COVID-19), whereas the rapid transmission and increased risk of COVID-19 has been linked to poor air quality and high levels of particulate matter. In this review, we focus on the mechanistic effects of environmental pollution on disease progression with special emphasis on the gut-lung axis.

Gut microbiota-derived metabolites in the regulation of host immune responses and immune-related inflammatory diseases

The gut microbiota has a critical role in the maintenance of immune homeostasis. Alterations in the intestinal microbiota and gut microbiota-derived metabolites have been recognized in many immune-related inflammatory disorders. These metabolites can be produced by gut microbiota from dietary components or by the host and can be modified by gut bacteria or synthesized de novo by gut bacteria. Gut microbiota-derived metabolites influence a plethora of immune cell responses, including T cells, B cells, dendritic cells, and macrophages. Some of these metabolites are involved in the pathogenesis of immune-related inflammatory diseases, such as inflammatory bowel diseases, diabetes, rheumatoid arthritis, and systemic lupus erythematosus. Here, we review the role of microbiota-derived metabolites in regulating the functions of different immune cells and the pathogenesis of chronic immune-related inflammatory diseases.

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.

New Insights Into the Cancer-Microbiome-Immune Axis: Decrypting a Decade of Discoveries

The past decade has witnessed groundbreaking advances in the field of microbiome research. An area where immense implications of the microbiome have been demonstrated is tumor biology. The microbiome affects tumor initiation and progression through direct effects on the tumor cells and indirectly through manipulation of the immune system. It can also determine response to cancer therapies and predict disease progression and survival. Modulation of the microbiome can be harnessed to potentiate the efficacy of immunotherapies and decrease their toxicity. In this review, we comprehensively dissect recent evidence regarding the interaction of the microbiome and anti-tumor immune machinery and outline the critical questions which need to be addressed as we further explore this dynamic colloquy.

Butyrate Shapes Immune Cell Fate and Function in Allergic Asthma

The microbiome plays a fundamental role in how the immune system develops and how inflammatory responses are shaped and regulated. The “gut-lung axis” is a relatively new term that highlights a crucial biological crosstalk between the intestinal microbiome and lung. A growing body of literature suggests that dysbiosis, perturbation of the gut microbiome, is a driving force behind the development, and severity of allergic asthma. Animal models have given researchers new insights into how gut microbe-derived components and metabolites, such as short-chain fatty acids (SCFAs), influence the development of asthma. While the full understanding of how SCFAs influence allergic airway disease remains obscure, a recurring theme of epigenetic regulation of gene expression in several immune cell compartments is emerging. This review will address our current understanding of how SCFAs, and specifically butyrate, orchestrates cell behavior, and epigenetic changes and will provide a detailed overview of the effects of these modifications on immune cells in the context of allergic airway disease.

Gut microbiome a promising target for management of respiratory diseases

The intestinal microbial flora has risen to be one of the important etiological factors in the development of diseases like colorectal cancer, obesity, diabetes, inflammatory bowel disease, anxiety and Parkinson's. The emergence of the association between bacterial flora and lungs led to the discovery of the gut-lung axis. Dysbiosis of several species of colonic bacteria such as Firmicutes and Bacteroidetes and transfer of these bacteria from gut to lungs via lymphatic and systemic circulation are associated with several respiratory diseases such as lung cancer, asthma, tuberculosis, cystic fibrosis, etc. Current therapies for dysbiosis include use of probiotics, prebiotics and synbiotics to restore the balance between various species of beneficial bacteria. Various approaches like nanotechnology and microencapsulation have been explored to increase the permeability and viability of probiotics in the body. The need of the day is comprehensive study of mechanisms behind dysbiosis, translocation of microbiota from gut to lung through various channels and new technology for evaluating treatment to correct this dysbiosis which in turn can be used to manage various respiratory diseases. Microfluidics and organ on chip model are emerging technologies that can satisfy these needs. This review gives an overview of colonic commensals in lung pathology and novel systems that help in alleviating symptoms of lung diseases. We have also hypothesized new models to help in understanding bacterial pathways involved in the gut-lung axis as well as act as a futuristic approach in finding treatment of respiratory diseases caused by dysbiosis.

Metabolomic differences of exhaled breath condensate among children with and without asthma

BACKGROUND

There remains an unmet need in objective tests for diagnosing asthma in children. The objective of this study was to investigate the potential of metabolomic profiles of exhaled breath condensate (EBC) to discriminate stable asthma in Asian children in the community.

METHODS

One hundred and sixty-five Asian children (92 stable asthma and 73 non-asthmatic controls) participating in a population-based cohort were enrolled and divided into training and validation sets. Nuclear magnetic resonance-based metabolomic profiles of EBC samples were analyzed by using orthogonal partial least squares discriminant analysis.

RESULTS

EBC metabolomic signature (lactate, formate, butyrate, and isobutyrate) had an area under the receiver operator characteristic curve (AUC) of 0.826 in discriminating children with and without asthma in the training set, which significantly outperformed FeNO (AUC = 0.574; P < .001) and FEV₁ /FVC % predicted (AUC = 0.569; P < .001). The AUC for EBC metabolomic signature was 0.745 in the validation set, which was slightly but not significantly lower than in the testing set (P = .282). We further extrapolated two potentially involved metabolic pathways, including pyruvate (P = 1.67 × 10^-3 ; impact: 0.14) and methane (P = 1.89 × 10^-3 ; impact: 0.15), as the most likely divergent metabolisms between children with and without asthma.

CONCLUSION

This study provided evidence supporting the role of EBC metabolomic signature to discriminate stable asthma in Asian children in the community, with a discriminative property outperforming conventional clinical tests such as FeNO or spirometry.

Interleukin-9-secreting CD4+ T cells regulate CD8+ T cells cytotoxicity in patients with acute coronary syndromes

T cells play vital roles in the development and progression of acute coronary syndromes (ACS), including cytotoxicity mediated by CD8⁺ T cells and immunoregulatory activity mediated by CD4⁺ T cells. Interleukin (IL)-9-secreting CD4⁺ T cells (Th9 cells) were recently found to be involved in the onset of ACS. We investigated regulatory role of Th9 cells to CD8⁺ T cells in patients with stable angina pectoris, unstable angina pectoris, and acute myocardial infarction (AMI). Circulating Th9 cells percentage, plasma IL-9 level, and PU.1 mRNA relative level was up-regulated in AMI patients compared with controls. There was no significant difference of IL-9-secreting CD8⁺ T cells percentage among groups. CD8⁺ T cells from AMI patients revealed increased cytotoxicity than those from controls, which presented as enhanced cytotolytic activity to target cells, increased interferon-γ and tumor necrosis factor-α secretion, elevated perforin and granzyme B production, and reduced programmed death-1 and cytotoxic T lymphocyte-associated protein 4. IL-9 stimulation did not affect proliferation, but promoted CD8⁺ T-cell cytotoxicity from both controls and AMI patients. IL-9-secreting CD4⁺ T cells were enriched in CD4⁺ CCR4^- CCR6^- CXCR3^- cells. The enhancement of CD8⁺ T-cell cytotoxicity induced by CD4⁺ CCR4^- CCR6^- CXCR3^- cells was dependent on IL-9 secretion. The present results indicated that up-regulation of IL-9-secreting CD4⁺ T cells may contribute to pathogenesis of AMI through enhancement of CD8⁺ T-cell cytotoxicity.

Antibiotic use during pregnancy increases offspring asthma severity in a dose-dependent manner

BACKGROUND

The use of antibiotics during pregnancy is associated with increased allergic asthma risk in the offspring, and given that approximately 25% of pregnant women are prescribed antibiotics, it is important to understand the mechanisms contributing to this phenomenon. Currently, there are no studies that directly test this association experimentally. Our objective was to develop a mouse model in which antibiotic treatment during pregnancy results in increased offspring asthma susceptibility.

METHODS

Pregnant mice were treated daily from gestation day 8-17 with an oral solution of the antibiotic vancomycin, and three concentrations were tested. At weaning, offspring were subjected to an adjuvant-free experimental asthma protocol using ovalbumin as an allergen. The composition of the gut microbiome was determined in mothers and offspring with samples collected from five different time points; short-chain fatty acids were also analyzed in allergic offspring.

RESULTS

We found that maternal antibiotic treatment during pregnancy was associated with increased offspring asthma severity in a dose-dependent manner. Furthermore, maternal vancomycin treatment during pregnancy caused marked changes in the gut microbiome composition in both mothers and pups at several different time points. The increased asthma severity and intestinal microbiome changes in pups were also associated with significantly decreased cecal short-chain fatty acid concentrations.

CONCLUSION

Consistent with the "Developmental Origins Hypothesis," our results confirm that exposure to antibiotics during pregnancy shapes the neonatal intestinal environment and increases offspring allergic lung inflammation.

Go With Your Gut: The Shaping of T-Cell Response by Gut Microbiota in Allergic Asthma

Novel methods in immunological research and microbiome evaluation have dramatically changed several paradigms associated with the pathogenesis of allergic asthma (AAS). Ovalbumin and house dust mite-induced AAS in germ-free or specific pathogen-free mice are the two leading experimental platforms that significantly contribute to elucidate the relationship between AAS and gut microbiota. Beyond the exacerbation of T helper (Th) 2 responses, a complex network of immunological interaction driven by gut microbiota could modulate the final effector phase. Regulatory T cells are abundant in gastrointestinal mucosa and have been shown to be pivotal in AAS. The gut microbiota could also influence the activity of other T cell subsets such as Th9, Th17, and populations of effector/memory T lymphocytes. Furthermore, gut microbiota metabolites drive the hematopoietic pattern of dendritic cells and ameliorate lung Th2 immunity in AAS models. The administration of probiotics has shown conflicting results in AAS, and limited evidence is available on the immunological pathways beyond their activity. Moreover, the impact of early-life gut dysbiosis on AAS is well-known both experimentally and clinically, but discrepancies are observed between preclinical and clinical settings. Herein, our aim is to elucidate the most relevant preclinical and clinical scenarios to enlighten the potential role of the gut microbiota in modulating T lymphocytes activity in AAS.

Obesity as a risk factor for COVID-19: an overview

The current coronavirus disease-2019 (COVID-19) pandemic presents a huge challenge for health-care systems worldwide. Many different risk factors are associated with disease severity, such as older age, diabetes, hypertension, and most recently obesity. The incidence of obesity has been on the rise for the past 25 years, reaching over 2 billion people throughout the world, and obesity itself could be considered a pandemic. In this review, we summarize aspects involved with obesity, such as changes in the immune response, nutritional factors, physiological factors, and the gut-lung axis, that impact the viral response and the COVID-19 prognosis.

Alterations in the Gut Microbiome and Suppression of Histone Deacetylases by Resveratrol Are Associated with Attenuation of Colonic Inflammation and Protection Against Colorectal Cancer

Inflammatory bowel disease (IBD) is known to significantly increase the risk for development of colorectal cancer (CRC), suggesting inflammation and cancer development are closely intertwined. Thus, agents that suppress inflammation may prevent the onset of cancer. In the current study, we used resveratrol, an anti-inflammatory stilbenoid, to study the role of microbiota in preventing inflammation-driven CRC. Resveratrol treatment in the azoxymethane (AOM) and dextran sodium sulphate (DSS) CRC murine model caused an increase in anti-inflammatory CD4 + FOXP3 + (Tregs) and CD4 + IL10 + cells, a decrease in proinflammatory Th1 and Th17 cells, and attenuated CRC development. Gut microbial profile studies demonstrated that resveratrol altered the gut microbiome and short chain fatty acid (SCFA), with modest increases in n-butyric acid and a potential butyrate precursor isobutyric acid. Fecal transfer from resveratrol-treated CRC mice and butyrate supplementation resulted in attenuation of disease and suppression of the inflammatory T cell response. Data also revealed both resveratrol and sodium butyrate (BUT) were capable of inhibiting histone deacetylases (HDACs), correlating with Treg induction. Analysis of The Cancer Genome Atlas (TCGA) datasets revealed increased expression of Treg-specific transcription factor FoxP3 or anti-inflammatory IL-10 resulted in an increase in 5-year survival of patients with CRC. These data suggest that alterations in the gut microbiome lead to an anti-inflammatory T cell response, leading to attenuation of inflammation-driven CRC.

Host dysbiosis negatively impacts IL-9-producing T-cell differentiation and antitumour immunity

BACKGROUND

Host-microbiota interactions shape T-cell differentiation and promote tumour immunity. Although IL-9-producing T cells have been described as potent antitumour effectors, their role in microbiota-mediated tumour control remains unclear.

METHODS

We analysed the impact of the intestinal microbiota on the differentiation of colonic lamina propria IL-9-producing T cells in germ-free and dysbiotic mice. Systemic effects of the intestinal microbiota on IL-9-producing T cells and the antitumour role of IL-9 were analysed in a model of melanoma-challenged dysbiotic mice.

RESULTS

We show that germ-free mice have lower frequency of colonic lamina propria IL-9-producing T cells when compared with conventional mice, and that intestinal microbiota reconstitution restores cell frequencies. Long-term antibiotic treatment promotes host dysbiosis, diminishes intestinal IL-4 and TGF-β gene expression, decreases the frequency of colonic lamina propria IL-9-producing T cells, increases the susceptibility to tumour development and reduces the frequency of IL-9-producing T cells in the tumour microenvironment. Faecal transplant restores intestinal microbiota diversity, and the frequency of IL-9-producing T cells in the lungs of dysbiotic animals, restraining tumour burden. Finally, recombinant IL-9 injection enhances tumour control in dysbiotic mice.

CONCLUSIONS

Host-microbiota interactions are required for adequate differentiation and antitumour function of IL-9-producing T cells.

Butyrate improves cardiac function and sympathetic neural remodeling following myocardial infarction in rats

Increased inflammation is found in cardiac sympathetic neural remodeling with malignant ventricular arrhythmia (VA) following myocardial infarction (MI). Butyrate, as a microbiota-derived short-chain fatty acid, can inhibit inflammation and myocardial hypertrophy. However, the role of butyrate in sympathetic neural remodeling after MI is unknown. This study aimed to investigate whether butyrate could improve cardiac dysfunction and VA following MI by regulating inflammation and sympathetic neural remodeling. MI rats were randomized to administrate the butyrate or vehicle through intraperitoneal injection to undergo the study. Our data demonstrated that butyrate treatment preserved the partial cardiac function at 7 days post-MI. Butyrate downregulated the expression of essential for inflammatory response in the infarct border zone at 3 days post-MI. Particularly, butyrate promoted expression of M2 macrophage markers. Increased expressions of nerve growth factor and norephinephrine at 7 days after MI were inhibited in butyrate-treated rats. Furthermore, butyrate significantly decreased the density of nerve fibers for growth-associated protein-43 and tyrosine hydroxylase and resulted in fewer episodes of inducible VA. In conclusion, butyrate administration ameliorated cardiac function and VA after MI possibly through promoting M2 macrophage polarization to suppress inflammatory responses and inhibit sympathetic neural remodeling and may present an effective pharmacological strategy for the prevention of MI-related remodeling.

Th9 cells in allergic diseases: A role for the microbiota?

Since their discovery about 10 years ago, Th9 cells have been increasingly linked to allergic pathologies. Within this review, we summarize the current knowledge on associations between Th9 cells and allergic diseases and acknowledge Th9 cells as important targets in future treatment of allergic diseases. However, until today, it is not fully understood how these Th9 cell responses are modulated. We describe current literature suggesting that these Th9 cell responses might be stimulated by microbial species such as Staphylococcus aureus and Candida albicans, while on the other hand, microbial and dietary compounds such as retinoic acid (RA), butyrate and vitamin D show suppressive capacity on allergy‐related Th9 responses. By reviewing this recent research, we provide new insights into the modulating capacity of the microbiota on Th9 cell responses. Consequently, microbial and dietary factors may be used as innovative tools to target Th9 cells in the treatment of allergic diseases. However, further research is needed to elucidate the mechanisms behind these interactions in order to translate this knowledge into clinical allergy settings.

T Helper 9 Cells: A New Player in Immune-Related Diseases

The helper T cell 9 (Thelper-9, Th9), as a functional subgroup of CD4⁺T cells, was first discovered in 2008. Th9 cells expressed transcription factor PU.1 and cytokine interleukin-9 (IL-9) characteristically. Recent researches have shown that the differentiation of Th9 cells was coregulated by cytokine transforming growth factor β, IL-4, and various transcription factors. Th9 cells, as a new player, played an important role in various immune-related diseases, including tumors, inflammatory diseases, parasite infection, and other diseases. In this article, we summarize the related research progress and discuss the possible prospect.

Roseburia intestinalis supernatant ameliorates colitis induced in mice by regulating the immune response

Inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn's disease (CD), has a complex etiology that may be associated with dysbiosis of the microbiota. Previously, our study revealed significant loss of Roseburia intestinalis from the gut of untreated patients with CD, and that R. intestinalis exerted anti-inflammatory functions in TNBS-induced colitis; however, the function of R. intestinalis supernatant is unknown. Therefore, LPS-induced macrophages, including RAW264.7 macrophages and bone marrow-derived macrophages were treated with R. intestinalis supernatant. The results indicated that R. intestinalis supernatant suppressed expression of interleukin (IL)-6 and signal transducer and activator of transcription 3 (STAT3) by macrophages. Additionally, these findings were further verified in vivo in DSS- and TNBS-induced mouse models of colitis. It was observed that R. intestinalis supernatant ameliorated IBD colitis by reducing the number of inflammatory macrophages and Th17 cells in the colon, and by downregulating the expression of IL-6 and STAT3. Finally, the non-protein components of R. intestinalis supernatant were examined using gas chromatography-mass spectrometry analysis and identified the presence of short-chain fatty acids. In conclusion, the results of the present study indicated that R. intestinalis supernatant may regulate immune responses and ameliorate colitis.