Postbiotic-Enabled Targeting of the Host-Microbiota-Pathogen Interface: Hints of Antibiotic Decline?

A Critical Review of Postbiotics as Promising Novel Therapeutic Agents for Clostridial Infections

Clostridial infections, known for their severity and rapid progression, present significant challenges in both clinical and veterinary fields. These bacteria, which can survive without oxygen and produce protective spores, cause many diseases, ranging from simple gastrointestinal disorders to severe and potentially fatal infections including botulism, tetanus, and gas gangrene. The rising occurrence of antibiotic-resistant strains and the repetitive character of some Clostridial illnesses, including Clostridioides difficile infections (CDI), highlight the immediate need for alternate treatment approaches. Postbiotics, which are metabolites derived from probiotics, are showing great potential as effective agents against these diseases. The current study offers a comprehensive investigation of the potential of postbiotics as therapeutic agents for treating Clostridial infections, including C. difficile, Clostridium perfringens, Clostridium botulinum, and Clostridium tetani. It also examines the processes by which postbiotics exert their effects. Preliminary investigations have shown that postbiotics have promising antibacterial and antibiofilm properties, indicating their potential as adjunct agents in methods for controlling microbial growth. Nevertheless, more study is required to thoroughly demonstrate their medicinal uses.

Postbiotics as a therapeutic tool in Alzheimer's disease: Insights into molecular pathways and neuroprotective effects

Alzheimer's disease (AD) is a progressive neurodegenerative disease, characterized by oxidative stress, neuroinflammation, mitochondrial dysfunction, neurotransmitter imbalance, tau hyperphosphorylation, and amyloid beta (Aβ) accumulation in brain regions. The gut microbiota (GM) has a major impact on brain function due to its bidirectional interaction with the gut through the gut-brain axis. The gut dysbiosis has been associated with neurological disorders, emphasizing the importance of gut homeostasis in maintaining appropriate brain function. The changes in the composition of microbiomes influence neuroinflammation and Aβ accumulation by releasing pro-inflammatory cytokines, decreasing gut and blood-brain barrier (BBB) integrity, and microglial activation in the brain. Postbiotics, are bioactive compounds produced after fermentation, have been shown to provide several health benefits, particularly in terms of neuroinflammation and cognitive alterations associated with AD. Several research studies on animal models and human have successfully proven the effects of postbiotics on enhancing cognition and memory in experimental animals. This article explores the protective effects of postbiotics on cellular mechanisms responsible for AD pathogenesis and studies highlighting the influence of postbiotics as a total combination and specific compounds, including short-chain fatty acids (SCFAs). In addition, postbiotics act as a promising option for future research to deal with AD's progressive nature and improve an individual's life quality using microbiota modulation.

Indole-3-Aldehyde alleviates lung inflammation in COPD through activating Aryl Hydrocarbon Receptor to inhibit HDACs/NF-κB/NLRP3 signaling pathways

Indole-3-aldehyde (I3A) is an intestinal microbial metabolite that regulates inflammation in various inflammatory diseases; however, its role in chronic obstructive pulmonary disease (COPD) remains unclear. This study aimed to investigate the anti-inflammatory effects and molecular mechanisms of I3A in COPD. We constructed in vivo models using cigarette smoke (CS)-stimulated mice and in vitro models using cigarette smoke extract (CSE)-stimulated MH-S cells. The results demonstrated that I3A significantly alleviated bronchial obstruction in mice with COPD and reduced the expression of inflammatory factors such as TNF-α, IL-1β, and IL-6. Additionally, I3A decreased the levels of matrix metalloproteinases MMP2, MMP12, and inhibited the NF-κB p65/NLRP3 pathways. Further investigation revealed that I3A inhibited NF-κB activity by suppressing p65 phosphorylation and nuclear translocation in CSE-stimulated MH-S cells. The activation of the NF-κB and NLRP3 signaling pathways is mediated by histone deacetylase 5 (HDAC5) and HDAC6, both of which are inhibited by I3A. Subsequent experiments indicated that aryl hydrocarbon receptor (AHR) knockdown attenuated the inhibitory effect of I3A on pro-inflammatory cytokines and the HDACs/NF-κB/NLRP3 signaling pathways, highlighting the dependence of I3A's anti-inflammatory effects on the AHR receptor. KEY MESSAGES: I3A effectively reduced lung inflammation in COPD mice by inhibiting the NF-κB pathway. In CSE-stimulated MH-S cells, I3A suppressed p65 phosphorylation and nuclear translocation, thereby inhibiting NF-κB activity. The activation of the NF-κB/NLRP3 pathways by HDAC5 and HDAC6 was diminished by I3A. Through the activation of the AHR receptor, I3A suppressed the activities of HDAC5/6, leading to a decrease in inflammatory factor levels.

Human and gut microbiota synergy in a metabolically active superorganism: a cardiovascular perspective

Despite significant advances in diagnosis and treatment over recent decades, cardiovascular disease (CVD) remains one of the leading causes of morbidity and mortality in Western countries. This persistent burden is partly due to the incomplete understanding of fundamental pathogenic mechanisms, which limits the effectiveness of current therapeutic interventions. In this context, recent evidence highlights the pivotal role of immuno-inflammatory activation by the gut microbiome in influencing cardiovascular disorders, potentially opening new therapeutic avenues. Indeed, while atherosclerosis has been established as a chronic inflammatory disease of the arterial wall, accumulating data suggest that immune system regulation and anti-inflammatory pathways mediated by gut microbiota metabolites play a crucial role in a range of CVDs, including heart failure, pericardial disease, arrhythmias, and cardiomyopathies. Of particular interest is the emerging understanding of how tryptophan metabolism-by both host and microbiota-converges on the Aryl hydrocarbon Receptor (AhR), a key regulator of immune homeostasis. This review seeks to enhance our understanding of the role of the immune system and inflammation in CVD, with a focus on how gut microbiome-derived tryptophan metabolites, such as indoles and their derivatives, contribute to cardioimmunopathology. By exploring these mechanisms, we aim to facilitate the development of novel, microbiome-centered strategies for combating CVD.

Postbiotics: the new horizons of microbial functional bioactive compounds in food preservation and security

In recent decades, consumers, manufacturers, and researchers have been more interested in functional foods, which include probiotics, prebiotics, and postbiotics. Probiotics are live microbes that, when regulated in enough quantities, provide health benefits on the host, while the prebiotics are substrates that host microorganisms selectively use. Postbiotics are metabolites and cell-wall components that are beneficial to the host and are released by living bacteria or after lysis. Postbiotic dietary supplements are more stable than probiotics and prebiotics. Many bioactivities of postbiotics are unknown or poorly understood. Hence, this study aims to present a synopsis of the regular elements and new developments of the postbiotics including health-promoting effects, production, conceptualization of terms, bioactivities, and applications in the field of food safety and preservation. Postbiotics aid in bio preservation and the reduction of biofilm development in food due to their organic acids, bacteriocins, and other antibacterial activities. The present study examines the production of postbiotic metabolites in situ in food and the effects of external and internal food components. The antimicrobial roles, removal of biofilms, and its applications in preservation and food safety have also been discussed. This paper also explored the various aspects like manipulation of postbiotic composition in the food system and its safety measures.

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Feed additives of bacterial origin as an immunoprotective or imunostimulating factor

Since January 2006 when using antibiotics as growth promoters in animal feed have been banned scientists are looking for the best resolution to apply alternative substances. Extensive research into the health-promoting properties of probiotics and prebiotics has led to significant interest in the mechanisms of action of the combined administration of these feed additives as a synbiotic. Subsequent research has led to the development of new products. Among the most important health benefits of additives are, inhibiting the growth of pathogenic bacteria in the GI tract, maintenance of homeostasis, treatment of inflammatory bowel diseases, and increase in immunity. Specific immunomodulatory mechanisms of action are not well understood and the effect is not always positive, though there are no reports of adverse effects of these substances found in the literature. For this reason, research is still being conducted on their proper application. However, due to the difficulties of carrying out research on humans, evidence of the beneficial effect of these additives comes mainly from experiments on animals. The objective of the present work was to assess the effect of probiotics, prebiotics, and synbiotics, as well as new additives including postbiotics, proteobiotics, nutribiotics, and pharmabiotics, on specific immunomodulatory mechanisms of action, increase in immunity, the reduction of a broad spectrum of diseases.

Role of Postbiotics in Diet-Induced Metabolic Disorders

Although the prevalence of metabolic disorders has progressively increased over the past few decades, metabolic disorders can only be effectively treated with calorie restriction and improved physical activity. Recent research has focused on altering the gut microbiome using prebiotics, probiotics, and postbiotics because various metabolic syndromes are caused by gut microbial dysbiosis. Postbiotics, substances produced or released by microorganism metabolic activities, play an important role in maintaining and restoring host health. Because postbiotics have a small amount of literature on their consumption, there is a need for more experiments on short- and long-term intake. This review discusses current postbiotic research, categories of postbiotics, positive roles in metabolic syndromes, and potential therapeutic applications. It covers postbiotic pleiotropic benefits, such as anti-obesity, anti-diabetic, and anti-hypertensive qualities, that could aid in the management of metabolic disorders. Postbiotics are promising tools for developing health benefits and therapeutic goals owing to their clinical, technical, and economic properties. Postbiotic use is attractive for altering the microbiota; however, further studies are needed to determine efficacy and safety.

Molecular and Cellular Mechanisms Influenced by Postbiotics

In recent years, commensal bacteria colonizing the human body have been recognized as important determinants of health and multiple pathologic conditions. Among the most extensively studied commensal bacteria are the gut microbiota, which perform a plethora of functions, including the synthesis of bioactive products, metabolism of dietary compounds, and immunomodulation, both through attenuation and immunostimulation. An imbalance in the microbiota population, i.e., dysbiosis, has been linked to many human pathologies, including various cancer types and neurodegenerative diseases. Targeting gut microbiota and microbiome-host interactions resulting from probiotics, prebiotics, and postbiotics is a growing opportunity for the effective treatment of various diseases. As more research is being conducted, the microbiome field is shifting from simple descriptive analysis of commensal compositions to more molecular, cellular, and functional studies. Insight into these mechanisms is of paramount importance for understanding and modulating the effects that microbiota, probiotics, and their derivatives exert on host health.

Gut Microbial Metabolite-Mediated Regulation of the Intestinal Barrier in the Pathogenesis of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease. The disease has a multifactorial aetiology, involving genetic, microbial as well as environmental factors. The disease pathogenesis operates at the host-microbe interface in the gut. The intestinal epithelium plays a central role in IBD disease pathogenesis. Apart from being a physical barrier, the epithelium acts as a node that integrates environmental, dietary, and microbial cues to calibrate host immune response and maintain homeostasis in the gut. IBD patients display microbial dysbiosis in the gut, combined with an increased barrier permeability that contributes to disease pathogenesis. Metabolites produced by microbes in the gut are dynamic indicators of diet, host, and microbial interplay in the gut. Microbial metabolites are actively absorbed or diffused across the intestinal lining to affect the host response in the intestine as well as at systemic sites via the engagement of cognate receptors. In this review, we summarize insights from metabolomics studies, uncovering the dynamic changes in gut metabolite profiles in IBD and their importance as potential diagnostic and prognostic biomarkers of disease. We focus on gut microbial metabolites as key regulators of the intestinal barrier and their role in the pathogenesis of IBD.

Development and in vitro-in vivo performances of an inhalable indole-3-carboxaldehyde dry powder to target pulmonary inflammation and infection

A tryptophan metabolite of microbial origin, indole-3-carboxaldehyde (3-IAld), has been recently identified as a Janus molecule that, acting at the host-pathogen interface and activating the aryl hydrocarbon receptor, can result as a potential candidate to treat infections as well as diseases with an inflammatory and/or immune component. In this work, an inhaled dry powder of 3-IAld was developed and evaluated for its efficacy, compared to oral and intranasal administration using an aspergillosis model of infection and inflammation. The obtained inhalable dry powder was shown to: i) be suitable to be delivered for pulmonary administration, ii) possess good toxicological safety, and iii) be superior to other administration modalities (oral and intranasal) in reducing disease scores by acting on infection and inflammation. This study supports the use of 3-IAld inhalable dry powders as a potential novel therapeutic tool to target inflammation and infection in pulmonary diseases.

A Shifted Composition of the Lung Microbiota Conditions the Antifungal Response of Immunodeficient Mice

The microbiome, i.e., the communities of microbes that inhabit the surfaces exposed to the external environment, participates in the regulation of host physiology, including the immune response against pathogens. At the same time, the immune response shapes the microbiome to regulate its composition and function. How the crosstalk between the immune system and the microbiome regulates the response to fungal infection has remained relatively unexplored. We have previously shown that strict anaerobes protect from infection with the opportunistic fungus Aspergillus fumigatus by counteracting the expansion of pathogenic Proteobacteria. By resorting to immunodeficient mouse strains, we found that the lung microbiota could compensate for the lack of B and T lymphocytes in Rag1^–/– mice by skewing the composition towards an increased abundance of protective anaerobes such as Clostridia and Bacteroidota. Conversely, NSG mice, with major defects in both the innate and adaptive immune response, showed an increased susceptibility to infection associated with a low abundance of strict anaerobes and the expansion of Proteobacteria. Further exploration in a murine model of chronic granulomatous disease, a primary form of immunodeficiency characterized by defective phagocyte NADPH oxidase, confirms the association of lung unbalance between anaerobes and Proteobacteria and the susceptibility to aspergillosis. Consistent changes in the lung levels of short-chain fatty acids between the different strains support the conclusion that the immune system and the microbiota are functionally intertwined during Aspergillus infection and determine the outcome of the infection.

Targeted Drug Delivery Technologies Potentiate the Overall Therapeutic Efficacy of an Indole Derivative in a Mouse Cystic Fibrosis Setting

Inflammation plays a major role in the pathophysiology of cystic fibrosis (CF), a multisystem disease. Anti-inflammatory therapies are, therefore, of interest in CF, provided that the inhibition of inflammation does not compromise the ability to fight pathogens. Here, we assess whether indole-3-aldehyde (3-IAld), a ligand of the aryl hydrocarbon receptor (AhR), may encompass such an activity. We resorted to biopharmaceutical technologies in order to deliver 3-IAld directly into the lung, via dry powder inhalation, or into the gut, via enteric microparticles, in murine models of CF infection and inflammation. We found the site-specific delivery of 3-IAld to be an efficient strategy to restore immune and microbial homeostasis in CF organs, and mitigate lung and gut inflammatory pathology in response to fungal infections, in the relative absence of local and systemic inflammatory toxicity. Thus, enhanced delivery to target organs of AhR agonists, such as 3-IAld, may pave the way for the development of safe and effective anti-inflammatory agents in CF.

In the Age of Viral Pandemic, Can Ingredients Inspired by Human Milk and Infant Nutrition Be Repurposed to Support the Immune System?

In 2020, with the advent of a pandemic touching all aspects of global life, there is a renewed interest in nutrition solutions to support the immune system. Infants are vulnerable to infection and breastfeeding has been demonstrated to provide protection. As such, human milk is a great model for sources of functional nutrition ingredients, which may play direct roles in protection against viral diseases. This review aims to summarize the literature around human milk (lactoferrin, milk fat globule membrane, osteopontin, glycerol monolaurate and human milk oligosaccharides) and infant nutrition (polyunsaturated fatty acids, probiotics and postbiotics) inspired ingredients for support against viral infections and the immune system more broadly. We believe that the application of these ingredients can span across all life stages and thus apply to both pediatric and adult nutrition. We highlight the opportunities for further research in this field to help provide tangible nutrition solutions to support one's immune system and fight against infections.

Postbiotics against Pathogens Commonly Involved in Pediatric Infectious Diseases

The Sustainable Development goals for 2020 included reducing all causes associated with infant and perinatal mortality in their priorities. The use of compounds with bioactive properties has been proposed as a therapeutic strategy due to their stimulating effect on the host's immune system. Additionally, biotherapeutic products such as postbiotics, tentatively defined as compounds produced during a fermentation process that support health and well-being, promote intestinal barrier integrity without posing considerable risks to children's health. Although this is a concept in development, there are increasing studies in the field of nutrition, chemistry, and health that aim to understand how postbiotics can help prevent different types of infections in priority populations such as minors under the age of five. The present review aims to describe the main mechanisms of action of postbiotics. In addition, it presents the available current evidence regarding the effects of postbiotics against pathogens commonly involved in pediatric infections. Postbiotics may constitute a safe alternative capable of modulating the cellular response and stimulating the host's humoral response.