Redox signaling mediates symbiosis between the gut microbiota and the intestine

Gut redox and microbiome: charting the roadmap to T-cell regulation

The gastrointestinal (GI) tract redox environment, influenced by commensal microbiota and bacterial-derived metabolites, is crucial in shaping T-cell responses. Specifically, metabolites from gut microbiota (GM) exhibit robust anti-inflammatory effects, fostering the differentiation and regulation of CD8+ tissue-resident memory (TRM) cells, mucosal-associated invariant T (MAIT) cells, and stabilizing gut-resident Treg cells. Nitric oxide (NO), a pivotal redox mediator, emerges as a central regulator of T-cell functions and gut inflammation. NO impacts the composition of the gut microbiome, driving the differentiation of pro-inflammatory Th17 cells and exacerbating intestinal inflammation, and supports Treg expansion, showcasing its dual role in immune homeostasis. This review delves into the complex interplay between GI redox balance and GM metabolites, elucidating their profound impact on T-cell regulation. Additionally, it comprehensively emphasizes the critical role of GI redox, particularly reactive oxygen species (ROS) and NO, in shaping T-cell phenotype and functions. These insights offer valuable perspectives on disease mechanisms and potential therapeutic strategies for conditions associated with oxidative stress. Understanding the complex cross-talk between GI redox, GM metabolites, and T-cell responses provides valuable insights into potential therapeutic avenues for immune-mediated diseases, underscoring the significance of maintaining GI redox balance for optimal immune health.

Ethoxyquin attenuates enteric oxidative stress and inflammation by promoting cytokine expressions and symbiotic microbiota in heat-stressed broilers

Intestinal oxidative stress in broilers is produced by chronic heat stress (HS) and has a negative impact on poultry performance as it induces intestinal inflammation and promotes the invasion of gram-negative bacteria, such as bacterial lipopolysaccharide (LPS). Therefore, dietary inclusion of the antioxidant compound, ethoxyquin (EQ), could improve enteric antioxidant capacity, immune responses, and the epithelial barrier, and maintain the symbiotic gut microbiota community. To investigate the effects of EQ supplementation on alleviating enteric oxidative stress in heat-stressed broilers, 200 one-day-old male Ross 308 broilers were randomly assigned to 4 groups (n = 50 chicks/group; n = 10 chicks/replicate) and fed a basal diet supplemented with 0 (CT), 50 (EQ-50), 100 (EQ-100), and 200 (EQ-200) mg EQ/ kg-1 for 5 wk. The chicks were raised in floor pens inside the broiler farm at a temperature and humidity index (THI) of 29 from d 21 to d 35. Growth performance traits, relative organ index, hepatic antioxidant enzymes, serum immunity, total adenylate, and cytokine activities were improved in the EQ-50 group (linear or quadratic P < 0.05), promoting the relative mRNA expression of cytokine gene-related anti-inflammatory and growth factors. A distinct microbial community colonised the gut microbiota in the EQ-50 group, with a high relative abundance of Lactobacillus, Ligilactobacillus, Limosilactobacillus, Pediococcus, Blautia, and Faecalibacterium compared to the other groups. Dietary supplementation with 50 mg EQ/ kg-1 for 5 wk attenuates enteric oxidative stress and intestinal inflammation by enhancing serum immune and cytokine content (IgG, IL-6, and TGF-β,) and symbiotic microbiota in heat-stressed broilers. EQ promotes the expression of Hsp70, SOD2, GPx 4, IL-6, and IGF-1 cytokine gene-related anti-inflammatory and growth factors in heat-stressed hepatic broilers. Collectively, EQ-50 could be a suitable feed supplement for attenuating enteric oxidative stress and intestinal inflammation, thereby promoting the productivity of heat-stressed broilers.

Sensitive delivery systems and novel encapsulation technologies for live biotherapeutic products and probiotics

Live biotherapeutic product (LBP), a type of biological product, holds promise for the prevention or treatment of metabolic disease and pathogenic infection. Probiotics are live microorganisms that improve the intestinal microbial balance and beneficially affect the health of the host when ingested in sufficient numbers. These biological products possess the advantages of inhibition of pathogens, degradation of toxins, and modulation of immunity. The application of LBP and probiotic delivery systems has attracted great interest to researchers. The initial used technologies for LBP and probiotic encapsulation are traditional capsules and microcapsules. However, the stability and targeted delivery capability require further improved. The specific sensitive materials can greatly improve the delivery efficiency of LBPs and probiotics. The specific sensitive delivery systems show advantages over traditional ones due to their better properties of biocompatibility, biodegradability, innocuousness, and stability. Moreover, some new technologies, including layer-by-layer encapsulation, polyelectrolyte complexation, and electrohydrodynamic technology, show great potential in LBP and probiotic delivery. In this review, novel delivery systems and new technologies of LBPs and probiotics were presented, and the challenges and prospects were explored in specific sensitive materials for LBP and probiotic delivery.

Gut microbiota influence frailty syndrome in older adults: mechanisms and therapeutic strategies

Frailty syndrome denotes a decreased capacity of the body to maintain the homeostasis and stress of the internal environment, which simultaneously increases the risk of adverse health outcomes in older adults, including disability, hospitalization, falls, and death. To promote healthy aging, we should find strategies to cope with frailty. However, the pathogenesis of frailty syndrome is not yet clear. Recent studies have shown that the diversity, composition, and metabolites of gut microbiota significantly changed in older adults with frailty. In addition, several frailty symptoms were alleviated by adjusting gut microbiota with prebiotics, probiotics, and symbiosis. Therefore, we attempt to explore the pathogenesis of frailty syndrome in older people from gut microbiota and summarize the existing interventions for frailty syndrome targeting gut microbiota, with the aim of providing timely and necessary interventions and assistance for older adults with frailty.

Mitochondrial Dysfunction in Metabolic Dysfunction Fatty Liver Disease (MAFLD)

Nonalcoholic fatty liver disease (NAFLD) has become an increasingly common disease in Western countries and has become the major cause of liver cirrhosis or hepatocellular carcinoma (HCC) in addition to viral hepatitis in recent decades. Furthermore, studies have shown that NAFLD is inextricably linked to the development of extrahepatic diseases. However, there is currently no effective treatment to cure NAFLD. In addition, in 2020, NAFLD was renamed metabolic dysfunction fatty liver disease (MAFLD) to show that its pathogenesis is closely related to metabolic disorders. Recent studies have reported that the development of MAFLD is inextricably associated with mitochondrial dysfunction in hepatocytes and hepatic stellate cells (HSCs). Simultaneously, mitochondrial stress caused by structural and functional disorders stimulates the occurrence and accumulation of fat and lipo-toxicity in hepatocytes and HSCs. In addition, the interaction between mitochondrial dysfunction and the liver-gut axis has also become a new point during the development of MAFLD. In this review, we summarize the effects of several potential treatment strategies for MAFLD, including antioxidants, reagents, and intestinal microorganisms and metabolites.

The influence of microbiota on ferroptosis in intestinal diseases

Ferroptosis is a distinctive form of iron-dependent necrotic cell death, characterized by excessive lipid peroxidation on cellular membranes and compromised cellular antioxidant defenses. Multiple metabolic pathways, including iron and lipid metabolism, as well as antioxidant systems, contribute to the execution of ferroptosis. The gut microbiota exerts regulatory effects on ferroptosis through its microbial composition, biological functions, and metabolites. Notably, most pathogenic bacteria tend to promote ferroptosis, thereby inducing or exacerbating diseases, while most probiotics have been shown to protect against cell death. Given microbiota colonization in the gut, an intimate association is found between intestinal diseases and microbiota. This review consolidates the essential aspects of ferroptotic processes, emphasizing key molecules and delineating the intricate interplay between gut microbiota and ferroptosis. Moreover, this review underscores the potential utility of gut microbiota modulation in regulating ferroptosis for the treatment of intestinal diseases.

The potential mechanism of gut microbiota-microbial metabolites-mitochondrial axis in progression of diabetic kidney disease

Diabetic kidney disease (DKD), has become the main cause of end-stage renal disease (ESRD) worldwide. Lately, it has been shown that the onset and advancement of DKD are linked to imbalances of gut microbiota and the abnormal generation of microbial metabolites. Similarly, a body of recent evidence revealed that biological alterations of mitochondria ranging from mitochondrial dysfunction and morphology can also exert significant effects on the occurrence of DKD. Based on the prevailing theory of endosymbiosis, it is believed that human mitochondria originated from microorganisms and share comparable biological characteristics with the microbiota found in the gut. Recent research has shown a strong correlation between the gut microbiome and mitochondrial function in the occurrence and development of metabolic disorders. The gut microbiome's metabolites may play a vital role in this communication. However, the relationship between the gut microbiome and mitochondrial function in the development of DKD is not yet fully understood, and the role of microbial metabolites is still unclear. Recent studies are highlighted in this review to examine the possible mechanism of the gut microbiota-microbial metabolites-mitochondrial axis in the progression of DKD and the new therapeutic approaches for preventing or reducing DKD based on this biological axis in the future.

Gut microbial genetic variation modulates host lifespan, sleep, and motor performance

Recent studies have shown that gut microorganisms can modulate host lifespan and activities, including sleep quality and motor performance. However, the role of gut microbial genetic variation in regulating host phenotypes remains unclear. In this study, we investigated the links between gut microbial genetic variation and host phenotypes using Saccharomyces cerevisiae and Drosophila melanogaster as research models. Our result suggested a novel role for peroxisome-related genes in yeast in regulating host lifespan and activities by modulating gut oxidative stress. Specifically, we found that deficiency in catalase A (CTA1) in yeast reduced both the sleep duration and lifespan of fruit flies significantly. Furthermore, our research also expanded our understanding of the relationship between sleep and longevity. Using a large sample size and excluding individual genetic background differences, we found that lifespan is associated with sleep duration, but not sleep fragmentation or motor performance. Overall, our study provides novel insights into the role of gut microbial genetic variation in regulating host phenotypes and offers potential new avenues for improving health and longevity.

Probiotics and Commensal Bacteria Metabolites Trigger Epigenetic Changes in the Gut and Influence Beneficial Mood Dispositions

The effect of the intestinal microbiome on the gut-brain axis has received considerable attention, strengthening the evidence that intestinal bacteria influence emotions and behavior. The colonic microbiome is important to health and the pattern of composition and concentration varies extensively in complexity from birth to adulthood. That is, host genetics and environmental factors are complicit in shaping the development of the intestinal microbiome to achieve immunological tolerance and metabolic homeostasis from birth. Given that the intestinal microbiome perseveres to maintain gut homeostasis throughout the life cycle, epigenetic actions may determine the effect on the gut-brain axis and the beneficial outcomes on mood. Probiotics are postulated to exhibit a range of positive health benefits including immunomodulating capabilities. Lactobacillus and Bifidobacterium are genera of bacteria found in the intestines and so far, the benefits afforded by ingesting bacteria such as these as probiotics to people with mood disorders have varied in efficacy. Most likely, the efficacy of probiotic bacteria at improving mood has a multifactorial dependency, relying namely on several factors that include the agents used, the dose, the pattern of dosing, the pharmacotherapy used, the characteristics of the host and the underlying luminal microbial environment (e.g., gut dysbiosis). Clarifying the pathways linking probiotics with improvements in mood may help identify the factors that efficacy is dependent upon. Adjunctive therapies with probiotics for mood disorders could, through DNA methylation molecular mechanisms, augment the intestinal microbial active cohort and endow its mammalian host with important and critical co-evolutionary redox signaling metabolic interactions, that are embedded in bacterial genomes, and that in turn can enhance beneficial mood dispositions.

Oxidative stress in metabolic diseases: current scenario and therapeutic relevance

The metabolic syndrome is a clustering condition of increased abdominal obesity in concert with hyperglycemia, insulin resistance, hypertension, and dyslipidemia. It confers higher risk of metabolic diseases such as diabetes and ischemic heart disease and has been observed to be associated with high morbidity and mortality. It is a progressive pathological process for diabetes-induced complications and appears to be multifactorial in origin. Several preclinical, clinical, and epidemiological reports have shown a persistent link between the metabolic syndrome and oxidative stress. There is pronounced imbalance between pro-oxidants and anti-oxidants with increased production of oxidizing molecules, depletion of anti-oxidants, and consequently accumulation of protein and lipid oxidation products in the cell in metabolic syndrome. The increased cellular pro-oxidant activity also results in altered molecular pathways, mitochondrial dysfunction, deregulation in cell cycle control, chromosomal aberrations, inflammation, and overall decreased biological activity as well as impairment of the antioxidant systems. Here, the focus of our review article will be on the formation of oxidative species, the interplay between metabolic syndrome and oxidative stress, and its potential implications in therapeutic approaches.

Design, development, and evaluation of a registry system for hyperbaric oxygen therapy: A methodological study

Background and Aims

Hyperbaric oxygen therapy (HBOT), utilizes 100% oxygen at pressures greater than sea-level atmospheric pressure, for the treatment of conditions in which the tissues starve for oxygen. The Undersea and Hyperbaric Medical Society (UHMS) has granted HBOT approval for the treatment of various conditions. On the other hand, applying informatics registry systems can improve care delivery, ameliorate outcomes, and reduce the costs and medical errors for the patients receiving HBOT treatment. Therefore, we aimed to design, develop, and evaluate a registry system for patients undergoing HBOT.

Methods

In the first phase, the conceptual and logical models were designed after conducting symposiums with experts and having other experts review the models. In the second phase, the system was developed on the web using ASP.NET  and C# programming languages frameworks. The last phase involved Nielsen's heuristic evaluation method for the system's usability. Five experts evaluated the system, including three health information management specialists and two medical informatics specialists.

Results

The hyperbaric patient information registry system (HPIRS) interacts with three types of users-a specialist physician, a nurse, and a system administrator. A scenario for each predefined activity was designed, and all the information was stored in the SQL servers. The five experts independently found 152 issues, of which 84 were duplicates. The 68 distinct issues of the system were then resolved.

Conclusions

The design and development of such registry systems can make data available and stored carefully to improve clinical care and medical research and decrease costs and errors. These registries can provide the healthcare systems with E-health applications, improved data management, more secure data transfer, and support for statistical reporting. The implemented heuristic evaluation method can also provide a low-cost and readily available system to fix the issues of the designed systems.

Network-Based Redox Communication Between Abiotic Interactive Materials

Recent observations that abiotic materials can engage in redox-based interactive communication motivates the search for new redox-active materials. Here we fabricated a hydrogel from a four-armed thiolated polyethylene glycol (PEG-SH) and the bacterial metabolite, pyocyanin (PYO). We show that: (i) the PYO-PEG hydrogel is reversibly redox-active; (ii) the molecular-switching and directed electron flow within this PYO-PEG hydrogel requires both a thermodynamic driving force (i.e., potential difference) and diffusible electron carriers that serve as nodes in a redox network; (iii) this redox-switching and electron flow is controlled by the redox network’s topology; and (iv) the ability of the PYO-PEG hydrogel to “transmit” electrons to a second insoluble redox-active material (i.e., a catechol-PEG hydrogel) is context-dependent (i.e., dependent on thermodynamic driving forces and appropriate redox shuttles). These studies provide an experimental demonstration of important features of redox-communication and also suggest technological opportunities for the fabrication of interactive materials.

•

Thiol-pyocyanin reaction was used to create a redox-active and interactive hydrogel

•

The electron flow and molecular switching requires diffusible mediators

•

These mediators and pyocyanin hydrogel serve as “nodes” in a redox reaction network

•

The networked flow of electrons between two separated hydrogels is reported

Nonalcoholic Fatty Liver Disease and the Gut-Liver Axis: Exploring an Undernutrition Perspective

Nonalcoholic fatty liver disease (NAFLD) is a chronic condition affecting one quarter of the global population. Although primarily linked to obesity and metabolic syndrome, undernutrition and the altered (dysbiotic) gut microbiome influence NAFLD progression. Both undernutrition and NAFLD prevalence are predicted to considerably increase, but how the undernourished gut microbiome contributes to hepatic pathophysiology remains far less studied. Here, we present undernutrition conditions with fatty liver features, including kwashiorkor and micronutrient deficiency. We then review the gut microbiota-liver axis, highlighting key pathways linked to NAFLD progression within both overnutrition and undernutrition. To conclude, we identify challenges and collaborative possibilities of emerging multiomic research addressing the pathology and treatment of undernourished NAFLD.

Efficacy of probiotics on the modulation of gut microbiota in the treatment of diabetic nephropathy

Diabetic nephropathy (DN) is a major cause of end-stage renal disease, and therapeutic options for preventing its progression are insufficient. The number of patients with DN has been increasing in Asian countries because of westernization of dietary lifestyle, which may be associated with the following changes in gut microbiota. Alterations in the gut microbiota composition can lead to an imbalanced gastrointestinal environment that promotes abnormal production of metabolites and/or inflammatory status. Functional microenvironments of the gut could be changed in the different stages of DN. In particular, altered levels of short chain fatty acids, D-amino acids, and reactive oxygen species biosynthesis in the gut have been shown to be relevant to the pathogenesis of the DN. So far, evidence suggests that the gut microbiota may play a key role in determining networks in the development of DN. Interventions directing the gut microbiota deserve further investigation as a new protective therapy in DN. In this review, we discuss the potential roles of the gut microbiota and future perspectives in the protection and/or treatment of kidneys.

Intertwined Relationship of Mitochondrial Metabolism, Gut Microbiome and Exercise Potential

The microbiome has emerged as a key player contributing significantly to the human physiology over the past decades. The potential microbial niche is largely unexplored in the context of exercise enhancing capacity and the related mitochondrial functions. Physical exercise can influence the gut microbiota composition and diversity, whereas a sedentary lifestyle in association with dysbiosis can lead to reduced well-being and diseases. Here, we have elucidated the importance of diverse microbiota, which is associated with an individual's fitness, and moreover, its connection with the organelle, the mitochondria, which is the hub of energy production, signaling, and cellular homeostasis. Microbial by-products, such as short-chain fatty acids, are produced during regular exercise that can enhance the mitochondrial capacity. Therefore, exercise can be employed as a therapeutic intervention to circumvent or subside various metabolic and mitochondria-related diseases. Alternatively, the microbiome-mitochondria axis can be targeted to enhance exercise performance. This review furthers our understanding about the influence of microbiome on the functional capacity of the mitochondria and exercise performance, and the interplay between them.

Balancing reactive oxygen species generation by rebooting gut microbiota

Reactive oxygen species (ROS; free radical form O₂ ^•‾ , superoxide radical; OH^• , hydroxyl radical; ROO^• , peroxyl; RO^• , alkoxyl and non-radical form ¹ O₂ , singlet oxygen; H₂ O₂ , hydrogen peroxide) are inevitable companions of aerobic life with crucial role in gut health. But, overwhelming production of ROS can cause serious damage to biomolecules. In this review, we have discussed several sources of ROS production that can be beneficial or dangerous to the human gut. Microorganisms, organelles and enzymes play crucial role in ROS generation, where, NOX1 is the main intestinal enzyme, which produce ROS in the intestine epithelial cells. Previous studies have reported that probiotics play significant role in gut homeostasis by checking the ROS generation, maintaining the antioxidant level, immune system and barrier protection. With current knowledge, we have critically analyzed the available literature and presented the outcome in the form of bubble maps to suggest the probiotics that help in controlling the ROS-specific intestinal diseases, such as inflammatory bowel disease (IBD) and colon cancer. Finally, it has been concluded that rebooting of the gut microbiota with probiotics, postbiotics or fecal microbiota transplantation (FMT) can have crucial implications in the structuring of gut communities for the personalized management of the gastrointestinal (GI) diseases.

WORKbiota: A Systematic Review about the Effects of Occupational Exposure on Microbiota and Workers' Health

The characterization of human microbiota and the impact of its modifications on the health of individuals represent a current topic of great interest for the world scientific community. Scientific evidence is emerging regarding the role that microbiota has in the onset of important chronic illnesses. Since individuals spend most of their life at work, occupational exposures may have an impact on the organism's microbiota. The purpose of this review is to explore the influence that different occupational exposures have on human microbiota in order to set a new basis for workers' health protection and disease prevention. The literature search was performed in PubMed, Cochrane, and Scopus. A total of 5818 references emerged from the online search, and 31 articles were included in the systematic review (26 original articles and 5 reviews). Exposure to biological agents (in particular direct contact with animals) was the most occupational risk factor studied, and it was found involved in modifications of the microbiota of workers. Changes in microbiota were also found in workers exposed to chemical agents or subjected to work-related stress and altered dietary habits caused by specific microclimate characteristics or long trips. Two studies evaluated the role of microbiota changes on the development of occupational lung diseases. Occupational factors can interface with the biological rhythms of the bacteria of the microbiota and can contribute to its modifications and to the possible development of diseases. Future studies are needed to better understand the role of the microbiota and its connection with occupational exposure to promote projects for the prevention and protection of global health.

Altered microbiota-host metabolic cross talk preceding neutropenic fever in patients with acute leukemia

In 2 cohorts of patients with acute leukemia, Akkermansia expansion in the gut predicted a higher risk for neutropenic fever.

Metabolomics analysis suggested oxidative stress as the mediating pathway, thus offering potential targets for personalized prophylaxis.

Despite antibiotic prophylaxis, most patients with acute leukemia receiving mucotoxic chemotherapy develop neutropenic fever (NF), many cases of which remain without a documented etiology. Antibiotics disrupt the gut microbiota, with adverse clinical consequences, such as Clostridioides difficile infection. A better understanding of NF pathogenesis could inform the development of novel therapeutics without deleterious effects on the microbiota. We hypothesized that metabolites absorbed from the gut to the bloodstream modulate pyrogenic and inflammatory pathways. Longitudinal profiling of the gut microbiota in 2 cohorts of patients with acute leukemia showed that Akkermansia expansion in the gut was associated with an increased risk for NF. As a prototype mucolytic genus, Akkermansia may influence the absorption of luminal metabolites; thus, its association with NF supported our metabolomics hypothesis. Longitudinal profiling of the serum metabolome identified a signature associated with gut Akkermansia and 1 with NF. Importantly, these 2 signatures overlapped in metabolites in the γ-glutamyl cycle, suggesting oxidative stress as a mediator involved in Akkermansia-related NF. In addition, the level of gut microbial–derived indole compounds increased after Akkermansia expansion and decreased before NF, suggesting their role in mediating the anti-inflammatory effects of Akkermansia, as seen predominantly in healthy individuals. These results suggest that Akkermansia regulates microbiota-host metabolic cross talk by modulating the mucosal interface. The clinical context, including factors influencing microbiota composition, determines the type of metabolites absorbed through the gut barrier and their net effect on the host. Our findings identify novel aspects of NF pathogenesis that could be targets for precision therapeutics. This trial was registered at www.clinicaltrials.gov as #NCT03316456.

Efficacy and safety of hyperbaric oxygen therapy for moderate-to-severe ulcerative colitis: a protocol for a systematic review and meta-analysis

INTRODUCTION

Ulcerative colitis (UC) is a type of inflammatory bowel disease, and 62% of patients with UC felt that it is difficult for them to live a normal life. Furthermore, some researches have shown that about 15% of patients with UC undergo at least one extreme clinical course in their lifetime, and 10%-30% of patients with UC oblige colectomy. Although many investigations have demonstrated that HBO2 has a beneficial impact on UC treatment, a systematic review and meta-analysis are unavailable. Therefore, a meta-analysis is essential to assess the efficacy and safety of HBO2 in treating UC.

METHODS AND ANALYSIS

A systematic search plan will be performed in the following seven databases with a restriction of time from inception to September 2020 to filter the eligible studies: PubMed, Web of Science, Embase, Cochrane Library, China National Knowledge Infrastructure, Chinese Scientific Journal Database (VIP) and Chinese Biomedical Database WanFang. Other related resources will be also searched. Two independent reviewers will choose eligible researches and extract data. The risk of bias will be evaluated based on Cochrane Collaboration's Risk of Bias tool and Newcastle-Ottawa Scale. Eventually, a systematic review and meta-analysis will be performed via the Review Manager V.5.3 statistical software and STATA V.14.0 software.

ETHICS AND DISSEMINATION

This study will not involve the individual patient and any ethical problems since its outcomes are based on published data. Therefore, no ethical review and approval are required. We plan to publish the study in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42020210244.

Prophylactic effects of probiotics on respiratory viruses including COVID-19: a review

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is mainly transmitted through respiratory droplets. The symptoms include dry cough, fever, and fatigue; however, high propagation, mutation, and fatality rates have been reported for SARS-CoV-2. This review investigates the structure of SARS-CoV-2, antiviral mechanisms, preventive strategies, and remedies against it. Effective vaccines have been developed by Pfizer (95% effective), AstraZeneca (90% effective), Moderna (94.5% effective) vaccine, among others. However, herd immunity is also required. Probiotics play a major role in the gut health, and some are known to have therapeutic potential against viral infections. Their modes of antiviral activities include direct interaction with targeted viruses, production of antiviral metabolites, and immunomodulatory effects on the host. Hence, probiotics can be a useful prophylactic against COVID-19, and more studies are required on the effects of probiotics against other viral infections that may occur in future.

Understanding the Holobiont: Crosstalk Between Gut Microbiota and Mitochondria During Long Exercise in Horse

Endurance exercise has a dramatic impact on the functionality of mitochondria and on the composition of the intestinal microbiome, but the mechanisms regulating the crosstalk between these two components are still largely unknown. Here, we sampled 20 elite horses before and after an endurance race and used blood transcriptome, blood metabolome and fecal microbiome to describe the gut-mitochondria crosstalk. A subset of mitochondria-related differentially expressed genes involved in pathways such as energy metabolism, oxidative stress and inflammation was discovered and then shown to be associated with butyrate-producing bacteria of the Lachnospiraceae family, especially Eubacterium. The mechanisms involved were not fully understood, but through the action of their metabolites likely acted on PPARγ, the FRX-CREB axis and their downstream targets to delay the onset of hypoglycemia, inflammation and extend running time. Our results also suggested that circulating free fatty acids may act not merely as fuel but drive mitochondrial inflammatory responses triggered by the translocation of gut bacterial polysaccharides following endurance. Targeting the gut-mitochondria axis therefore appears to be a potential strategy to enhance athletic performance.

Matrix metalloproteinase 9 (MMP9) limits reactive oxygen species (ROS) accumulation and DNA damage in colitis-associated cancer

Colitis-associated cancer (CAC) is a subtype of colon cancer that is driven by chronic inflammation and is prevalent in chronic ulcerative colitis patients. The development of CAC is associated with the inflammation-dysplasia-carcinoma pathway which is significantly different than adenoma-carcinoma pathway of sporadic colon cancer (CRC). Matrix Metalloproteinase 9 (MMP9) is a zinc-dependent endopeptidase against extracellular matrix (ECM) proteins expressed in the gastrointestinal tract during inflammation. We have previously shown that MMP9 plays a tumor suppressor role in CAC via “MMP9-Notch1-ARF-p53 axis” pathway. The aim of this study is to determine the role of MMP9 in maintaining genomic stability in CAC. Homozygous transgenic mice with constitutive-expression of MMP9 in the colonic epithelium (TgM9) with their wild-type littermates (WT) and stably transfected HCT116 cells with/without MMP9 were used for in vivo and in vitro experiments, respectively. As ‘proof of concept’ model, nanoparticles (NPs) loaded with MMP9 siRNA were used to examine the effect of MMP9 silencing in the colonic epithelium. In CAC, colonic epithelium of TgM9 mice exhibited lower amounts of reactive oxygen species (ROS), less DNA damage, and increased expression of mismatch repair genes compared to WTs. Our study showed that MMP9 expression correlates with the reduced ROS levels, decreased DNA damage, and upregulated mismatch repair pathway. This suggests that MMP9 expression is a natural biological way to suppress CAC by limiting ROS accumulation and DNA damage in the colon. Therefore, MMP9 inhibition could be deleterious for CAC patient.

Microbiota-Mitochondria Inter-Talk: A Potential Therapeutic Strategy in Obesity and Type 2 Diabetes

The rising prevalence of obesity and type 2 diabetes (T2D) is a growing concern worldwide. New discoveries in the field of metagenomics and clinical research have revealed that the gut microbiota plays a key role in these metabolic disorders. The mechanisms regulating microbiota composition are multifactorial and include resistance to stress, presence of pathogens, diet, cultural habits and general health conditions. Recent evidence has shed light on the influence of microbiota quality and diversity on mitochondrial functions. Of note, the gut microbiota has been shown to regulate crucial transcription factors, coactivators, as well as enzymes implicated in mitochondrial biogenesis and metabolism. Moreover, microbiota metabolites seem to interfere with mitochondrial oxidative/nitrosative stress and autophagosome formation, thus regulating the activation of the inflammasome and the production of inflammatory cytokines, key players in chronic metabolic disorders. This review focuses on the association between intestinal microbiota and mitochondrial function and examines the mechanisms that may be the key to their use as potential therapeutic strategies in obesity and T2D management.

Environmental Exposures and Autoimmune Diseases: Contribution of Gut Microbiome

Environmental agents have been gaining more attention in recent years for their role in the pathogenesis of autoimmune diseases (ADs). Increasing evidence has linked environmental exposures, including trichloroethene (TCE), silica, mercury, pristane, pesticides, and smoking to higher risk for ADs. However, potential mechanisms by which these environmental agents contribute to the disease pathogenesis remains largely unknown. Dysbiosis of the gut microbiome is another important environmental factor that has been linked to the onset of different ADs. Altered microbiota composition is associated with impaired intestinal barrier function and dysregulation of mucosal immune system, but it is unclear if gut dysbiosis is a causal factor or an outcome of ADs. In this review article, we first describe the recent epidemiological and mechanistic evidences linking environmental/occupational exposures with various ADs (especially SLE). Secondly, we discuss how changes in the gut microbiome composition (dysbiosis) could contribute to the disease pathogenesis, especially in response to exposure to environmental chemicals.

Lactobacillus rhamnosus GG-induced Expression of Leptin in the Intestine Orchestrates Epithelial Cell Proliferation

BACKGROUND & AIMS

Identifying the functional elements that mediate efficient gut epithelial growth and homeostasis is essential for understanding intestinal health and disease. Many of these processes involve the Lactobacillus-induced generation of reactive oxygen species by NADPH oxidase (Nox1). However, the downstream signaling pathways that respond to Nox1-generated reactive oxygen species and mediate these events have not been described.

METHODS

Wild-type and knockout mice were fed Lactobacillus rhamnosus GG and the transcriptional and cell signaling pathway responses in the colon measured. Corroboration of data generated in mice was done using in organoid tissue culture and in vivo gut injury models.

RESULTS

Ingestion of L rhamnosus GG induces elevated levels of leptin in the gut epithelia, which as well as functioning in the context of metabolism, has pleiotropic activity as a chemokine that triggers cell proliferation. Consistently, using gut epithelial-specific knockout mice, we show that L rhamnosus GG-induced elevated levels of leptin is dependent on a functional Nox1 protein in the colonic epithelium, and that L rhamnosus GG-induced cell proliferation is dependent on Nox1, leptin, and leptin receptor. We also show that L rhamnosus GG induces the JAK-STAT signaling pathway in the gut in a Nox1, leptin, and leptin receptor-dependent manner.

CONCLUSIONS

These results demonstrate a novel role for leptin in the response to colonization by lactobacilli, where leptin functions in the transduction of signals from symbiotic bacteria to subepithelial compartments, where it modulates intestinal growth and homeostasis.

Feeding practice influences gut microbiome composition in very low birth weight preterm infants and the association with oxidative stress: A prospective cohort study

Knowledge about the development of the preterm infant gut microbiota is emerging and is critical to their health. Very-low-birth-weight (VLBW; birth weight, <1500 g) infants usually have special dietary needs while showing increased oxidative stress related to intensive care. This prospective cohort study assessed the effect of feeding practice on gut microbiome development and oxidative stress in preterm infants. Fecal samples were collected from each infant in the early (1-2 weeks of enteral feeding) and late (2-4 weeks of enteral feeding) feeding stages. We performed high-throughput sequencing of V3-V4 regions of the 16S rRNA gene to analyze the fecal microbiome composition of 20 VLBW preterm infants and to determine the association of gut bacterial composition with feeding practice using an oxidative stress marker (urinary F2-isoprostane). Our results showed that feeding practices in the late stage significantly influenced the gut microbiome composition and oxidative stress in preterm infants. Preterm infants fed human milk + human milk fortifier and only formula diets showed a significant increase in F2-isoprostane levels (P < 0.05) compared with those fed human milk + formula diet. The gut microbiome of the infants fed the human milk + Human milk fortifier diet showed the lower relative abundance of Veillonella (P < 0.05) compared with that of the infants fed the human milk + formula diet. The gut microbiome of the infants fed the only formula diet showed the lowest microbial diversity and the highest relative abundance of Terrisporobacter (P < 0.05) compared with the gut microbiome of the infants fed the other diets. Correlation network analysis showed that urinary F2-isoprostane level was positively correlated with Terrisporobacter and Enterobacteriaceae abundance (P < 0.05) in the preterm infants. In conclusion, these data suggest that feeding practice affects the bacterial diversity and composition in the gut microbiome and is associated with oxidative stress in VLBW preterm infants.

Sucrose metabolism alters Lactobacillus plantarum survival and interactions with the microbiota in the digestive tract

We investigated whether sucrose metabolism by probiotic Lactobacillus plantarum influences the intestinal survival and microbial responses to this organism when administered to mice fed a sucrose-rich, Western diet. A L. plantarum mutant unable to metabolize sucrose was constructed by deleting scrB, coding for beta-fructofuranosidase, in a rifampicin-resistant strain of L. plantarum NCIMB8826. The ScrB deficient mutant survived in 8-fold higher numbers compared to the wild-type strain when measured 24 h after administration on two consecutive days. According to 16S rRNA marker gene sequencing, proportions of Faecalibacterium and Streptococcus were elevated in mice fed the L. plantarum ΔscrB mutant. Metagenome predictions also indicated those mice contained a higher abundance of lactate dehydrogenases. This was further supported by a trend in elevated fecal lactate concentrations among mice fed the ΔscrB mutant. L. plantarum also caused other changes to the fecal metabolomes including higher concentrations of glycerol in mice fed the ΔscrB mutant and increased uracil, acetate and propionate levels among mice fed the wild-type strain. Taken together, these results suggest that sucrose metabolism alters the properties of L. plantarum in the digestive tract and that probiotics can differentially influence intestinal metabolomes via their carbohydrate consumption capabilities.

The microbiome and cognitive aging: a review of mechanisms

Gut microbiota plays an intrinsic role in communication between the gut and the brain and is capable of influencing the host brain by producing neurotransmitters and neurotrophins, the modulation of inflammatory processes amongst other key mechanisms. Increased age is also associated with changes in these key biological processes and impairments in a range of cognitive processes. We hypothesise several mechanisms in which gut microbiota may modulate changes in cognitive function with age. In this review, we discuss issues related to the measurement of cognition in the elderly and in particular outline a standardised model of cognition that could be utilised to better understand cognitive outcomes in future studies examining the relationship between gut microbiota and cognition in the elderly. We then review biological processes such as oxidative stress and inflammation which are related to cognitive changes with age and which are also influenced by our gut microbiota. Finally, we outline other potential mechanisms by which the gut microbiota may influence cognition.

Lactococcus Lactis Subsp. cremoris Is an Efficacious Beneficial Bacterium that Limits Tissue Injury in the Intestine

The use of beneficial bacteria to promote health is widely practiced. However, experimental evidence corroborating the efficacy of bacteria promoted with such claims remains limited. We address this gap by identifying a beneficial bacterium that protects against tissue damage and injury-induced inflammation in the gut. We first employed the Drosophila animal model to screen for the capacity of candidate beneficial bacteria to protect the fly gut against injury. From this screen, we identified Lactococcus lactis subsp. cremoris as a bacterium that elicited potent cytoprotective activity. Then, in a murine model, we demonstrated that the same strain confers powerful cytoprotective influences against radiological damage, as well as anti-inflammatory activity in a gut colitis model. In summary, we demonstrate the positive salutary effects of a beneficial bacterium, namely, L. lactis subsp. cremoris on intestinal tissue and propose the use of this strain as a therapeutic to promote intestinal health.

•

Drosophila can be used as an animal model to screen for beneficial bacteria

•

Lactococcus lactis subsp. cremoris elicited potent cytoprotection in the fly gut

•

L. lactis cremoris elicited anti-inflammatory activity in a mouse colitis model

•

L. lactis cremoris activated the cytoprotective Nrf2 pathway in flies and mice

Proteomic analysis of microbial induced redox-dependent intestinal signaling

Intestinal homeostasis is regulated in-part by reactive oxygen species (ROS) that are generated in the colonic mucosa following contact with certain lactobacilli. Mechanistically, ROS can modulate protein function through the oxidation of cysteine residues within proteins. Recent advances in cysteine labeling by the Isotope Coded Affinity Tags (ICATs) technique has facilitated the identification of cysteine thiol modifications in response to stimuli. Here, we used ICATs to map the redox protein network oxidized upon initial contact of the colonic mucosa with Lactobacillus rhamnosus GG (LGG). We detected significant LGG-specific redox changes in over 450 proteins, many of which are implicated to function in cellular processes such as endosomal trafficking, epithelial cell junctions, barrier integrity, and cytoskeleton maintenance and formation. We particularly noted the LGG-specific oxidation of Rac1, which is a pleiotropic regulator of many cellular processes. Together, these data reveal new insights into lactobacilli-induced and redox-dependent networks involved in intestinal homeostasis.

Hyperbaric oxygen therapy is well tolerated and effective for ulcerative colitis patients hospitalized for moderate-severe flares: a phase 2A pilot multi-center, randomized, double-blind, sham-controlled trial

BACKGROUND

Hyperbaric oxygen therapy (HBOT) markedly increases tissue oxygen delivery. Case series suggest it may have a potential therapeutic benefit in ulcerative colitis (UC). We investigated the therapeutic potential of HBOT as an adjunct to steroids for UC flares requiring hospitalization.

METHODS

The study was terminated early due to poor recruitment with 18 of the planned 70 patients enrolled. UC patients hospitalized for moderate-severe flares (Mayo score ≥6, endoscopic sub-score ≥2) were block randomized to steroids + daily HBOT (n = 10) or steroids + daily sham hyperbaric air (n = 8). Patients were blinded to study assignment, and assessments were performed by a blinded gastroenterologist. Primary outcome was the clinical remission rate at study day 5 (partial Mayo score ≤2 with no sub-score >1). Key secondary outcomes were: clinical response (reduction in partial Mayo score ≥2, rectal bleeding sub-score of 0-1) and progression to second-line therapy (colectomy or biologic therapy) during the hospitalization.

RESULTS

A significantly higher proportion of HBOT-treated patients achieved clinical remission at study day 5 and 10 (50 vs. 0%, p = 0.04). HBOT-treated patients less often required progression to second-line therapy during the hospitalization (10 vs. 63%, p = 0.04). The proportion requiring in-hospital colectomy specifically as second-line therapy for medically refractory UC was lower in the HBOT group compared to sham (0 vs. 38%, p = 0.07). There were no serious adverse events.

CONCLUSION

In this small, proof-of-concept, phase 2A trial, the use of HBOT as an adjunctive therapy to steroids for UC patients hospitalized for moderate-severe flares resulted in higher rates of clinical remission, and a reduction in rates of progression to second-line therapy during the hospitalization. Larger well-powered trials are needed, however, to provided definitive evidence of therapeutic benefit.

NoxO1 Controls Proliferation of Colon Epithelial Cells

Aim

Reactive oxygen species (ROS) produced by enzymes of the NADPH oxidase family serve as second messengers for cellular signaling. Processes such as differentiation and proliferation are regulated by NADPH oxidases. In the intestine, due to the exceedingly fast and constant renewal of the epithelium both processes have to be highly controlled and balanced. Nox1 is the major NADPH oxidase expressed in the gut, and its function is regulated by cytosolic subunits such as NoxO1. We hypothesize that the NoxO1-controlled activity of Nox1 contributes to a proper epithelial homeostasis and renewal in the gut.

Results

NoxO1 is highly expressed in the colon. Knockout of NoxO1 reduces the production of superoxide in colon crypts and is not subsidized by an elevated expression of its homolog p47phox. Knockout of NoxO1 increases the proliferative capacity and prevents apoptosis of colon epithelial cells. In mouse models of dextran sulfate sodium (DSS)-induced colitis and azoxymethane/DSS induced colon cancer, NoxO1 has a protective role and may influence the population of natural killer cells.

Conclusion

NoxO1 affects colon epithelium homeostasis and prevents inflammation.

Diet and microbiota linked in health and disease

Diet has shaped microbiota profiles through human evolution.

Skin-gut axis: The relationship between intestinal bacteria and skin health

The gut microbiome is an emerging area of interest in medicine. Imbalances in the gut microbiome have been linked to a number of disease states such as obesity and type 2 diabetes. The relationship between normally residing intestinal bacteria (the gut microbiota) and their potential role in the pathogenesis of skin diseases is an area of research for which we are only beginning to understand. Small studies have demonstrated underlying changes in the gut microbiome of patients with certain dermatological diseases. Interestingly, studies suggest that probiotics may have a role in the treatment of atopic dermatitis. However, the concept of the “skin-gut axis” is a newly emerging and important avenue of investigation, still lacking in pathobiological explanations. This review will introduce and describe the intestinal microbiome as it relates to skin health in a complex communication network between the immune system, endocrine system, metabolic system, and nervous system.

European contribution to the study of ROS: A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS)

The European Cooperation in Science and Technology (COST) provides an ideal framework to establish multi-disciplinary research networks. COST Action BM1203 (EU-ROS) represents a consortium of researchers from different disciplines who are dedicated to providing new insights and tools for better understanding redox biology and medicine and, in the long run, to finding new therapeutic strategies to target dysregulated redox processes in various diseases. This report highlights the major achievements of EU-ROS as well as research updates and new perspectives arising from its members. The EU-ROS consortium comprised more than 140 active members who worked together for four years on the topics briefly described below. The formation of reactive oxygen and nitrogen species (RONS) is an established hallmark of our aerobic environment and metabolism but RONS also act as messengers via redox regulation of essential cellular processes. The fact that many diseases have been found to be associated with oxidative stress established the theory of oxidative stress as a trigger of diseases that can be corrected by antioxidant therapy. However, while experimental studies support this thesis, clinical studies still generate controversial results, due to complex pathophysiology of oxidative stress in humans. For future improvement of antioxidant therapy and better understanding of redox-associated disease progression detailed knowledge on the sources and targets of RONS formation and discrimination of their detrimental or beneficial roles is required. In order to advance this important area of biology and medicine, highly synergistic approaches combining a variety of diverse and contrasting disciplines are needed.

MUC2 mucin deficiency alters inflammatory and metabolic pathways in the mouse intestinal mucosa

The mucus layer in the intestine affects several aspects of intestinal biology, encompassing physical, chemical protection, immunomodulation and growth, thus contributing to homeostasis. Mice with genetic inactivation of the Muc2 gene, encoding the MUC2 mucin, the major protein component of mucus, exhibit altered intestinal homeostasis, which is strictly dependent on the habitat, likely due to differing complements of intestinal microbes. Our previous work established that Muc2 deficiency was linked to low chronic inflammation resulting in tumor development in the small, large intestine including the rectum. Here, we report that inactivation of Muc2 alters metabolic pathways in the normal appearing mucosa of Muc2^-/- mice. Comparative analysis of gene expression profiling of isolated intestinal epithelial cells (IECs) and the entire intestinal mucosa, encompassing IECs, immune and stromal cells underscored that more than 50% of the changes were common to both sets of data, suggesting that most alterations were IEC-specific. IEC-specific expression data highlighted perturbation of lipid absorption, processing and catabolism linked to altered Pparα signaling in IECs. Concomitantly, alterations of glucose metabolism induced expression of genes linked to de novo lipogenesis, a characteristic of tumor cells. Importantly, gene expression alterations characterizing Muc2^-/- IECs are similar to those observed when analyzing the gene expression signature of IECs along the crypt-villus axis in WT B6 mice, suggesting that Muc2^-/- IECs display a crypt-like gene expression signature. Thus, our data strongly suggest that decreased lipid metabolism, and alterations in glucose utilization characterize the crypt proliferative compartment, and may represent a molecular signature of pre-neoplastic lesions.

Redox signaling mediated by the gut microbiota

The microbiota that inhabits the mammalian intestine can influence a range of physiological functions, including the modulation of immune responses, enhancement epithelial barrier function, and the stimulation of cell proliferation. While the mechanisms by which commensal prokaryotes stimulate immune signaling networks are well-characterized, less is known about the mechanistic control over homeostatic pathways within tissues. Recent reports by our research group have demonstrated that contact between the gut epithelia and some groups of enteric commensal bacteria prompts the rapid generation of reactive oxygen species (ROS) within host cells. Whereas the bacterial-induced production of ROS in phagocytes in response to ligand binding to Formyl Peptide Receptors (FPRs) and ensuing activation of NADPH oxidase 2 (Nox2) is a well-defined mechanism, ROS generated by other cell types such as intestinal epithelia in response to microbial signals via FPRs and the NADPH oxidase 1 (Nox1) is less appreciated. Importantly, enzymatically generated ROS have been shown to function as second messengers in many signal transduction pathways via the transient oxidative activity on sensor proteins bearing oxidant-sensitive thiol groups. Examples of redox sensitive proteins include tyrosine phosphatases that serve as regulators of MAPK pathways, focal adhesion kinase, as well as components involved NF-kB activation. Here, we review the leading edge discoveries gleaned from investigations that focus on microbial-induced generation of ROS and their functional effects on host physiology. These studies identify the functional molecular elements and mechanistic events that mediate the established effects of the normal microbiota on intestinal physiology.

The Influence of the Gut Microbiota on Host Physiology: In Pursuit of Mechanisms

The results generated from the NIH funded Human Microbiome Project (HMP) are necessarily tied to the overall mission of the agency, which is to foster scientific discoveries as a basis for protecting and improving health. The investment in the HMP phase 1 accomplished many of its goals including the preliminary characterization of the human microbiome and the identification of links between microbiome diversity and disease states. Going forward, the next step in these studies must involve the identification of the functional molecular elements that mediate the positive influence of a eubiotic microbiome on health and disease. This review will focus on recent advances describing mechanistic events in the intestine elicited by the microbiome. These include symbiotic bacteria-induced activation of redox-dependent cell signaling, the bacterial production of short chain fatty acids and ensuing cellular responses, and the secretion of bacteriocins by bacteria that have anti-microbial activities against potential pathogens.

The reduction of oxidative stress by nanocomposite Fullerol decreases mucositis severity and reverts leukopenia induced by Irinotecan

Irinotecan is a useful chemotherapeutic agent for the treatment of several solid tumors. However, this therapy is associated with side effects, including leukopenia and mucositis. Reactive oxygen species (ROS) activate inflammatory pathways and contribute to Irinotecan-induced mucositis. Fullerol is a nanocomposite with anti-oxidant properties that may reduce tissue damage after inflammatory stimuli. In this paper, the effects of Fullerol and mechanisms of protection were investigated in a model of Irinotecan-induced mucositis. Mucositis was induced by an injection of Irinotecan per 4 days in C57BL/6. Fullerol or a vehicle was injected every 12h. On day 7, the intestines were removed to evaluate histological changes, leukocyte influx, and the production of cytokines and ROS. Irinotecan therapy resulted in weight loss, an increased clinical score and intestinal injury. Treatment with Fullerol attenuated weight loss, decreased clinical score and intestinal damage. Irinotecan also induced increased ROS production in enterocytes, oxidative stress, IL-1β production, neutrophil and eosinophil influx in the ileum. Fullerol treatment decreased production of ROS in the enterocytes, oxidative stress, IL-1β production, neutrophil and eosinophil influx in the ileum. Irinotecan therapy also induced leukopenia in an ROS-dependent manner because leukopenia reverted in WT mice treated with Fullerol or Apocynin or in Gp91phox(-/-) mice. Mice treated with Irinotecan presented less melanoma tumor growth compared to the control group. Fullerol does not interfere in the anti-tumor action of Irinotecan. Fullerol has a great pharmacology potential to decreases the severity of mucositis and of leukopenia during chemotherapy treatment.

Control of Klebsiella pneumoniae pulmonary infection and immunomodulation by oral treatment with the commensal probiotic Bifidobacterium longum 5(1A)

Klebsiella pneumoniae (Kp) a common cause of pneumonia leads to intense lung injury and mortality that are correlated with infective exacerbations. Probiotics are a class of microorganisms that have immunomodulatory effects to benefit health. We investigated whether the probiotic Bifidobacterium longum 5(1A) induces protection in mice against lung infection induced by Kp and the potential involved mechanisms. Kp infection induced secretion of pro-inflammatory cytokines, neutrophil recruitment, significant bacterial load in the lung and 50% lethality. However, treatment with live B. longum 5(1A) induced faster resolution of inflammation associated with an increased production of IL-10, decreased lung damage with significantly reduction of bacterial burden that contributed to rescue 100% of mice from death. We found that these effects could be attributed, at least in part, to activation of the Toll-like receptor (TLR) adapter protein Mal, since B. longum 5(1A) treatment in Mal-deficient infected mice did not show the protection observed in wild type infected mice. Thus, we propose that live B. longum 5(1A) activates TLR-signaling pathway that results in ROS production and protects the host against pneumonia-induced death by finely tuning the inflammatory response and contributing to faster return to lung homeostasis.

Lactobacilli Modulate Epithelial Cytoprotection through the Nrf2 Pathway

An optimal gut microbiota influences many beneficial processes in the metazoan host. However, the molecular mechanisms that mediate and function in symbiont-induced host responses have not yet been fully characterized. Here, we report that cellular ROS enzymatically generated in response to contact with lactobacilli in both mice and Drosophila has salutary effects against exogenous insults to the intestinal epithelium via the activation of Nrf2 responsive cytoprotective genes. These data show that the xenobiotic-inducible Nrf2 pathway participates as a signaling conduit between the prokaryotic symbiont and the eukaryotic host. Indeed, our data imply that the capacity of lactobacilli to induce redox signaling in epithelial cells is a highly conserved hormetic adaptation to impel cellular conditioning to exogenous biotic stimuli. These data also highlight the role the microbiota plays in eukaryotic cytoprotective pathways and may have significant implications in the characterization of a eubiotic microbiota.

PRR-signaling pathways: Learning from microbial tactics

Recognition of bacterial pathogens by the mammalian host relies on the induction of early innate immune responses initiated by the activation of pattern-recognition receptors (PRRs) upon sensing of their cognate microbe-associated-patterns (MAMPs). Successful pathogens have evolved to intercept PRR activation and signaling at multiple steps. The molecular dissection of the underlying mechanisms revealed many of the basic mechanisms used by the immune system. Here we provide an overview of the different strategies used by bacterial pathogens and commensals to subvert and reprogram PPR-mediated innate immune responses. A particular attention is given to recent discoveries highlighting novel molecular details of the host inflammatory response in mammalian cells and current advances in our understanding of the interaction of commensals with PRR-mediated responses.

Involvement of the modulation of cancer cell redox status in the anti-tumoral effect of phenolic compounds

The association between the anti-tumoral properties of phenolics, the generation of ROS in culture medium and modulation of redox homeostasis was analyzed. In AGS cells, the anti-proliferative effect of quercetin was not reverted by catalase or SOD.

In vivo function and comparative genomic analyses of the Drosophila gut microbiota identify candidate symbiosis factors

Symbiosis is often characterized by co-evolutionary changes in the genomes of the partners involved. An understanding of these changes can provide insight into the nature of the relationship, including the mechanisms that initiate and maintain an association between organisms. In this study we examined the genome sequences of bacteria isolated from the Drosophila melanogaster gut with the objective of identifying genes that are important for function in the host. We compared microbiota isolates with con-specific or closely related bacterial species isolated from non-fly environments. First the phenotype of germ-free Drosophila (axenic flies) was compared to that of flies colonized with specific bacteria (gnotobiotic flies) as a measure of symbiotic function. Non-fly isolates were functionally distinct from bacteria isolated from flies, conferring slower development and an altered nutrient profile in the host, traits known to be microbiota-dependent. Comparative genomic methods were next employed to identify putative symbiosis factors: genes found in bacteria that restore microbiota-dependent traits to gnotobiotic flies, but absent from those that do not. Factors identified include riboflavin synthesis and stress resistance. We also used a phylogenomic approach to identify protein coding genes for which fly-isolate sequences were more similar to each other than to other sequences, reasoning that these genes may have a shared function unique to the fly environment. This method identified genes in Acetobacter species that cluster in two distinct genomic loci: one predicted to be involved in oxidative stress detoxification and another encoding an efflux pump. In summary, we leveraged genomic and in vivo functional comparisons to identify candidate traits that distinguish symbiotic bacteria. These candidates can serve as the basis for further work investigating the genetic requirements of bacteria for function and persistence in the Drosophila gut.

Redox signaling mediated by the gut microbiota

The microbiota that occupies the mammalian intestine can modulate a range of physiological functions, including control over immune responses, epithelial barrier function, and cellular proliferation. While commensal prokaryotic organisms are well known to stimulate inflammatory signaling networks, less is known about control over homeostatic pathways. Recent work has shown that gut epithelia contacted by enteric commensal bacteria rapidly generate reactive oxygen species (ROS). While the induced production of ROS in professional phagocytes via stimulation of formyl peptide receptors (FPRs) and activation of NADPH oxidase 2 (Nox2) is a well-studied process, ROS are also similarly elicited in other cell types, including intestinal epithelia, in response to microbial signals via FPRs and the epithelial NADPH oxidase 1 (Nox1). ROS generated by Nox enzymes have been shown to function as critical second messengers in multiple signal transduction pathways via the rapid and transient oxidative inactivation of a distinct class of sensor proteins bearing oxidant-sensitive thiol groups. These redox-sensitive proteins include tyrosine phosphatases that serve as regulators of MAP kinase pathways, focal adhesion kinase, as well as components involved in NF-κB activation. As microbe-elicited ROS has been shown to stimulate cellular proliferation and motility, and to modulate innate immune signaling, we hypothesize that many of the established effects of the normal microbiota on intestinal physiology may be at least partially mediated by this ROS-dependent mechanism.