Faecalibacterium prausnitzii subspecies-level dysbiosis in the human gut microbiome underlying atopic dermatitis

Extracellular vesicles of Limosilactobacillus fermentum SLAM216 ameliorate skin symptoms of atopic dermatitis by regulating gut microbiome on serotonin metabolism

Atopic dermatitis (AD) is a globally prevalent chronic inflammatory skin disorder. Its pathogenesis remains incompletely understood, resulting in considerable therapeutic challenges. Recent studies have highlighted the significance of the interaction between AD and gut microbiome. In this study, we investigated the effects of probiotic-derived extracellular vesicles on AD. Initially, we isolated and characterized extracellular vesicles from Limosilactobacillus fermentum SLAM 216 (LF216EV) and characterized their composition through multi-omics analysis. Gene ontology (GO) and pathway analysis classified LF216EV proteins into biological processes, molecular functions, and cellular components. Importantly, specific abundance in linoleic, oleic, palmitic, sebacic, and stearic acids indicating upregulated fatty acid metabolism were observed by metabolomic analysis. Furthermore, featured lipid profiling including AcylGlcADG and ceramide were observed in LF216EV. Importantly, in an atopic dermatitis-like cell model induced by TNFα/IFNγ, LF216EV significantly modulated the expression of immune regulatory genes (TSLP, TNFα, IL-6, IL-1β, and MDC), indicating its potential functionality in atopic dermatitis. LF216EV alleviated AD-like phenotypes, such as redness, scaling/dryness, and excoriation, induced by DNCB. Histopathological analysis revealed that LF216EV decreased epidermal thickness and mast cell infiltration in the dermis. Furthermore, LF216EV administration reduced mouse scratching and depression-related behaviors, with a faster onset than the classical treatment with dexamethasone. In the quantitative real-time polymerase chain reaction (qRT-PCR) analysis, we observed a significant increase in the expression levels of htrb2c, sert, and tph-1, genes associated with serotonin, in the skin and gut of the LF216EV-treated group, along with a significant increase in the total serum serotonin levels. Gut microbiome analysis of the LF216EV-treated group revealed an altered gut microbiota profile. Correlation analysis revealed that the genera Limosilactobacillus and Desulfovibrio were associated with differences in the intestinal metabolites, including serotonin. Our findings demonstrate that LF216EV mitigates AD-like symptoms by promoting serotonin synthesis through the modulation of gut microbiota and metabolome composition.

Faecalibacterium prausnitzii regulates carbohydrate metabolic functions of the gut microbiome in C57BL/6 mice

The probiotic impact of microbes on host metabolism and health depends on both host genetics and bacterial genomic variation. Faecalibacterium prausnitzii is the predominant human gut commensal emerging as a next-generation probiotic. Although this bacterium exhibits substantial intraspecies diversity, it is unclear whether genetically distinct F. prausnitzii strains might lead to functional differences in the gut microbiome. Here, we isolated and characterized a novel F. prausnitzii strain (UT1) that belongs to the most prevalent but underappreciated phylogenetic clade in the global human population. Genome analysis showed that this butyrate-producing isolate carries multiple putative mobile genetic elements, a clade-specific defense system, and a range of carbohydrate catabolic enzymes. Multiomic approaches were used to profile the impact of UT1 on the gut microbiome and associated metabolic activity of C57BL/6 mice at homeostasis. Both 16S rRNA and metagenomic sequencing demonstrated that oral administration of UT1 resulted in profound microbial compositional changes including a significant enrichment of Lactobacillus, Bifidobacterium, and Turicibacter. Functional profiling of the fecal metagenomes revealed a markedly higher abundance of carbohydrate-active enzymes (CAZymes) in UT1-gavaged mice. Accordingly, UT1-conditioned microbiota possessed the elevated capability of utilizing starch in vitro and exhibited a lower availability of microbiota-accessible carbohydrates in the gut. Further analysis uncovered a functional network wherein UT1 reduced the abundance of mucin-degrading CAZymes and microbes, which correlated with a concomitant reduction of fecal mucin glycans. Collectively, our results reveal a crucial role of UT1 in facilitating the carbohydrate metabolism of the gut microbiome and expand our understanding of the genetic and phenotypic diversity of F. prausnitzii.

The gut-skin axis: a bi-directional, microbiota-driven relationship with therapeutic potential

This review explores the emerging term "gut-skin axis" (GSA), describing the bidirectional signaling that occurs between the skin and the gastrointestinal tract under both homeostatic and disease conditions. Central to GSA communication are the gut and skin microbiota, the microbial communities that colonize these barrier surfaces. By influencing diverse host pathways, including innate immune, vitamin D receptor, and Aryl hydrocarbon receptor signaling, a balanced microbiota contributes to both tissue homeostasis and host defense. In contrast, microbiota imbalance, or dysbiosis at one site, can lead to local barrier dysfunction, resulting in the activation of signaling pathways that can disrupt tissue homeostasis at the other site, potentially leading to inflammatory skin conditions such as atopic dermatitis and psoriasis, or gut diseases like Inflammatory Bowel Disease. To date, most research on the GSA has examined the impact of the gut microbiota and diet on skin health, but recent studies show that exposing the skin to ultraviolet B-light can beneficially modulate both the gut microbiome and intestinal health. Thus, despite the traditional focus of clinicians and researchers on these organ systems as distinct, the GSA offers new opportunities to better understand the pathogenesis of cutaneous and gastrointestinal diseases and promote health at both sites.

It Takes a Village: Juvenile Idiopathic Arthritis and the Microbiome

Multiple risk factors for juvenile idiopathic arthritis (JIA) influence the microbiome, and various differences in the oral and fecal microbiome have been described to date in JIA. This review summarizes what is known and discusses potential implications for future research on the microbiome in JIA.

Advances of the exposome at individual levels and prevention in atopic dermatitis

Atopic dermatitis (AD), or eczema, is an inflammatory skin disease related to environmental factors. As a heterogeneous disease, it presents with complex phenotypes and endotypes. A variety of intrinsic and extrinsic factors can promote the development of AD. While there has been extensive discussion on environmental exposure at the population and community levels, discourse on exposome at individual levels in AD remains insufficient. For example, allergens, microorganisms, parasites, dietary factors, and psychological factors such as stress and anxiety play important roles in AD development. Microorganisms, in particular, exhibit altered composition and diversity on the skin of AD patients, influencing skin barrier integrity and immune responses. The impact of certain microorganisms, such as fungi and viruses, on AD has garnered increasing attention because of their important role in maintaining skin homeostasis. Dietary factors, including sugar intake and histamine-rich foods, may modulate AD risk and severity, although findings are controversial. Allergens, particularly house dust mite allergens, and aeroallergens, exacerbate AD symptoms by promoting inflammation and barrier dysfunction. Since AD is often the first step in the atopic march, its primary prevention measures are crucial. Some preventive measures involving microorganisms, diet, and moisturizers remain controversial. Effective preventive strategies necessitate a clear understanding of the complex mechanisms of AD, especially host-microbe-environment interactions. This review summarizes recent advances in understanding various risk and protective factors, as well as primary prevention measures for AD.

Faecalibacterium Diversity in the Gut Microbiome of Crohn's Disease Patients

Faecalibacterium has recently garnered attention for its potential health implications. To better understand its role, we developed and assessed real-time PCR assays for detecting and quantifying various Faecalibacterium species in human stool samples from both healthy individuals and Crohn's disease patients, either in flare or remission. The assays targeted the Microbial Anti-inflammatory Molecule (MAM) genes, which encode MAM proteins. These assays demonstrated 100% species-specificity using strains from six Faecalibacterium species: Faecalibacterium prausnitzii, Faecalibacterium taiwanense, Faecalibacterium duncaniae, Faecalibacterium longum, Faecalibacterium hattori, and Faecalibacterium CNCM4541. They also showed high sensitivity with detection limits of 10^5 bacteria per gram of sample. In healthy individuals, the different Faecalibacterium species varied in abundance. F. taiwanense, F. duncaniae, and F. longum were the most prevalent, around 10^10 bacteria/g of stool. In contrast, F. hattori and CNCM4541 were less abundant, with 10^7 bacteria/g. Despite its low abundance, F. hattori was present in all healthy subjects, while CNCM4541 was detected in only 50% of them. Notably, F. taiwanense, F. duncaniae, and F. longum were found in all healthy individuals. In Crohn's disease patients, both in flare and remission, a decrease in Faecalibacterium species was observed, with no recovery in remission. The most abundant species in Crohn's disease patients were F. prausnitzii and F. duncaniae, around 10^7 bacteria/g, while F. longum, F. hattori, and F. taiwanense were present at lower levels (10^6 bacteria/g), and CNCM4541 was no longer detected. Interestingly, F. prausnitzii showed a smaller decrease in abundance compared with other species. Moreover, F. prausnitzii was significantly more prevalent in patients in remission than in those in flare, suggesting that it may be more resistant to inflammation. These findings highlight the importance of accurately characterizing and quantifying Faecalibacterium species to better understand their role in health and disease.

The impact of prebiotics, probiotics and synbiotics on the prevention and treatment of atopic dermatitis in children: an umbrella meta-analysis

Background

Studies have suggested that the administration of prebiotics, probiotics and synbiotics (pre-, pro-, and synbiotics) may potentially decrease the incidence of atopic dermatitis (AD) and alleviate its severity in children; however, recent studies have yielded inconclusive findings.

Objective

This umbrella meta-analysis aimed to comprehensively assess the effect of pre-, pro-, and synbiotics on AD among children.

Methods

A systematic search was carried out in the PubMed and Scopus databases up to April 2024 to identify relevant meta-analyses. Relative risks (RR) and weighted mean differences (WMD) along with their 95% confidence intervals (CI) were pooled using a random effects model to evaluate the impacts on both the incidence of AD and its severity, as assessed by the Scoring Atopic Dermatitis (SCORAD) index.

Results

This umbrella meta-analysis included 38 meta-analyses, with 127,150 participants. The analysis suggested that intervention with pre-, pro-, and synbiotics significantly reduced the incidence of AD (RR = 0.74, 95% CI: 0.70-0.79), which was confirmed by subgroup analyses. The treatment significantly reduced SCORAD score (WMD = -3.75, 95% CI: -5.08 to -2.42). In subgroup analysis, multi-strain probiotics, Lactobacillus, synbiotics, and pre-, pro-, and synbiotics mixtures were found to significantly decrease the SCORAD score, while, Bifidobacterium and prebiotics alone did not show a significant effect on the SCORAD score. The treatment resulted in a significant decrease in SCORAD score among children with moderate to severe AD, but not in subjects with mild AD.

Conclusions

Probiotics and synbiotics could be promising interventions to reduce the risk of developing AD and alleviate its severity in children.

Compositional and Functional Profile of Gut Microbiota in a Cohort of Adult Spanish Patients with Atopic Dermatitis Using Metagenomics: A Cross-Sectional Study

Background: The role of gut dysbiosis in the pathophysiology of atopic dermatitis (AD) through immune system (IS) imbalance is a novel line of investigation currently under discussion. This study aimed to characterize compare the composition and functional profile of the gut microbiota (GM) between adults with AD and healthy individuals. Methods: Observational cross-sectional study, where fecal samples from 70 adults (38 patients and 32 controls) were analyzed using metagenomics and bioinformatics. Results: Differences between the GM of patients with AD and healthy individuals were demonstrated. Reduced microbial diversity was found in subjects with AD. Bacterial species with lower abundance primarily belonged to the families Ruminococcaceae, Akkermansiaceae, and Methanobacteriaceae. Several microbial metabolic pathways were found to be decreased in patients with AD, including amino acid biosynthesis, vitamin biosynthesis, fatty acids and lipids biosynthesis, and energy metabolism. Conclusion: Adults with AD exhibited a distinct GM compared to healthy individuals. Changes were demonstrated both compositionally and functionally. Further investigation is mandatory to elucidate the potential link and causal relationship between gut dysbiosis and AD, which may be crucial for a deeper understanding of the disease's pathophysiology and the development of novel therapeutic approaches.

Atopic Dermatitis and Atopic Keratoconjunctivitis: New Insights in the Analyses of Microbiota and Probiotic Effect

Atopy is defined as a predisposition to hypersensitivity reactions against a range of antigens. It is characterized by the activation of CD4+ T helper type 2 (Th2) cells and an increased production of immunoglobulin E (IgE). The most common atopic conditions are atopic dermatitis, asthma, allergic rhinitis, food allergies, and atopic ocular diseases. Atopic keratoconjunctivitis (AKC) is a chronic, bilateral inflammatory condition affecting the ocular surface, frequently occurring in conjunction with atopic dermatitis. It is not uncommon for patients to present with multiple conditions simultaneously or in a sequential manner. A comprehensive understanding of the underlying mechanisms of atopic diseases is essential for the effective clinical evaluation and treatment. Recent research has underscored the pivotal role of the microbiota in the pathogenesis of atopic dermatitis and atopic eye diseases, with alterations in microbial composition (dysbiosis) being linked to a spectrum of atopic conditions. Probiotics are currently being investigated as a potential treatment option for restoring microbial balance and alleviating disease symptoms. This review examines the relationship between atopic dermatitis, atopic keratoconjunctivitis, and the microbiota, evaluating the current evidence and exploring the potential of probiotics as a novel therapeutic approach.

Effects of the Curcuminoid and Non-Curcuminoid Compounds of Turmeric on the Gut Microbiome and Inflammation: Potential Use in the Treatment and Prevention of Disease

The gut microbiome is a complex system that directly interacts with and influences many systems in the body. This delicate balance of microbiota plays an important role in health and disease and is highly influenced by lifestyle factors and the surrounding environment. As further research emerges, understanding the full potential of the gut microbiome and the impact of using nutraceuticals to positively influence its function may open the door to greater therapeutic outcomes in the treatment and prevention of disease. Curcumin, a bioactive compound derived from the turmeric rhizome, has been studied in depth for its influence on human health as a potent anti-inflammatory and antioxidant properties. However, the therapeutic activity of curcumin is limited by its low oral bioavailability. While most available research has primarily focused on the curcuminoid compounds of turmeric, the non-curcuminoid compounds hold promise to offer therapeutic benefits while synergistically enhancing the bioavailability of curcumin and supporting the gut microbiome. This review summarizes current knowledge of the relationship between the gut and the various systems within the body, and how dysbiosis, or disruption in the gut microbial balance, leads to inflammation and increased risk of chronic disease. The review also summarizes recent research that focuses on the bioactivity of both the curcuminoid and non-curcuminoid compounds that comprise the whole turmeric root and their synergistic role in enhancing bioavailability to support a healthy gut microbiome and promising use in the treatment and prevention of disease.

Gut microbiota and plasma metabolites in pregnant mothers and infant atopic dermatitis: A multi-omics study

Background

Many studies reported the influence of infants' gut microbiota on atopic dermatitis (AD) postnatally, yet the role of maternal gut microbiota and plasma metabolites in infants' AD remains largely unexplored.

Methods

Sixty-three pregnant mother-infants were enrolled and followed after childbirth in Guangzhou, China. Demographic information, maternal stool and plasma samples, and records for infants' AD were collected. Maternal gut microbiota/metabolome and plasma metabolome were profiled using shotgun metagenomics and non-targeted metabolomics. Logistic regression and multi-omics analysis were used to explore characteristic maternal gut microbiota in the AD and health groups.

Results

The α-diversity of maternal gut microbiota in health group was significantly higher than AD group (Shannon diversity P = 0.02, Simpson diversity P = 0.04). Short-chain fatty acids (SCFAs) producing microorganisms, including Faecalibacterium, Roseburia, Butyricicoccus, and Ruminococcus, as well as the abundance of phenylalanine, tyrosine, and tryptophan biosynthesis pathway, were enriched in health group (LDA>2 and P < 0.05). Virulent factors (VFs) involved in immune modulation were enriched in the health group, while VFs involving in adhesin were enriched in the AD group (P < 0.05). Metabolomic analysis showed that a polyunsaturated fatty acid/linoleic acid, 13S-hydroxyoctadecadienoic, were negatively associated with AD in both the gut and plasma samples (FDR<0.05). Several other linoleic acids and flavonoids were negatively associated with AD (FDR<0.05). Neural network analysis revealed that microorganisms enriched in health group may produce these protective fatty acids.

Conclusions

Our findings show that maternal gut microorganisms/metabolites and plasma metabolites during pregnancy impact subsequent pathogenesis of infants AD. This illuminates new strategies against early AD in offspring.

Gut Dysbiosis and Adult Atopic Dermatitis: A Systematic Review

Background/Objectives: Research on the relationship between gut microbiota (GM) and atopic dermatitis (AD) has seen a growing interest in recent years. The aim of this systematic review was to determine whether differences exist between the GM of adults with AD and that of healthy adults (gut dysbiosis). Methods: We conducted a systematic review based on the PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). The search was performed using PubMed, EMBASE, and Web of Science. Observational and interventional studies were analyzed. Results: Although the studies showed heterogeneous results, some distinguishing characteristics were found in the intestinal microbial composition of adults with dermatitis. Even though no significant differences in diversity were found between healthy and affected adults, certain microorganisms, such as Bacteroidales, Enterobacteriaceae, and Clostridium (perfringens), were more characteristic of the fecal microbiota in adults with AD. Healthy individuals exhibited lower abundances of aerobic bacteria and higher abundances of short-chain fatty acid-producing species and polyamines. Clinical trials showed that the consumption of probiotics (Bifidobacterium and/or Lactobacillus), fecal microbiota transplants, and balneotherapy modified the fecal microbiota composition of participants and were associated with significant improvements in disease management. Conclusions: In anticipation of forthcoming clinical trials, it is essential to conduct meta-analyses that comprehensively evaluate the effectiveness and safety of interventions designed to modify intestinal flora in the context of AD. Preliminary evidence suggests that certain interventions may enhance adult AD management.

Hotspots and development trends of gut microbiota in atopic dermatitis: A bibliometric analysis from 1988 to 2024

BACKGROUND

Atopic dermatitis (AD) is a prevalent inflammatory skin condition that commonly occurs in children. More and more scientific evidence suggests that gut microbiota plays an important role in the pathogenesis of AD, whereas there is no article providing a comprehensive summary and analysis. We aimed to analyze documents on AD and gut microbiota and identify hotspots and development trends in this field.

METHODS

Articles and reviews in the field of AD and gut microbiota from January 1, 1988 to October 20, 2024 were obtained from the Web of Science Core Collection database. Biblioshiny was utilized for evaluating and visualizing the core authors, journals, countries, documents, trend topics, and hotspots in this field.

RESULTS

Among 1672 documents, it indicated that the number of annual publications generally increased. The United States had the highest production, impact, and international collaboration. Journal of Allergy and Clinical Immunology was the journal of the maximum publications. Based on keyword co-occurrence and clustering analysis, "stratum-corneum lipids," "probiotics," "prebiotics," "fecal microbiota transplantation," "phage therapy," "short chain fatty-acids," "biologic therapy," and "skin inflammation" represented current trend topics. The pathological and molecular mechanisms and associated therapeutic methods for AD and gut microbiota were the research hotspots. The incorporation of microbiota-based therapies alongside conventional treatments can contribute to better clinical outcomes.

CONCLUSION

We highlighted that gut microbiota may exacerbate symptoms of AD through various aspects, including immunity, metabolites, and neuroendocrine pathways. More efforts are required to investigate the safety and efficacy of gut microbial management methods for the prevention and treatment of AD.

Fecal microbiota transplantation as a new way for OVA-induced atopic dermatitis of juvenile mice

Children all over the world suffer from atopic dermatitis (AD), a prevalent condition that impairs their health. Corticosteroids, which have long-term negative effects, are frequently used to treat AD. There has been a growing body of research on the gut microbiota's function in AD. Nevertheless, the function and underlying mechanisms of fecal microbiota transplantation (FMT) in AD children remain to be established. Therefore, in order to assess the preventive effects of FMT treatment on AD and investigate the mechanisms, we constructed an ovalbumin (OVA)-induced juvenile mouse AD model in this investigation. This study explored the role and mechanism of FMT treatment in AD through 16S RNA sequencing, pathological histological staining, molecular biology, and Flow cytometry. Results demonstrated that the FMT treatment improved the gut microbiota's diversity and composition, bringing it back to a level similar to that of a close donor. Following FMT treatment, OVA-specific antibodies were inhibited, immunoglobulin (Ig) E production was decreased, the quantity of mast cells and eosinophils was decreased, and specific inflammatory markers in the skin and serum were decreased. Further mechanistic studies revealed that FMT treatment induced CD103+ DCs and programmed cell death ligand 1 (PD-L1)/programmed cell death 1 (PD-1) expression in skin-draining lymph nodes and promoted Treg production to induce immune tolerance and suppress skin inflammation. Meanwhile, changes in the gut microbiota were substantially correlated with Th2 cytokines, OVA-specific antibodies, and PD-L1/PD-1. In conclusion, FMT regulates the Th1/Th2 immunological balance and the gut microbiota. It may also inhibit AD-induced allergy responses through the PD-L1/PD-1 pathway, and providing a unique idea and possibly a fresh approach to the treatment of AD.

Alterations of gut microbiome in eosinophilic chronic rhinosinusitis

PURPOSE

A growing body of evidence has elucidated that the gut microbiota has a crucial impact on the pathophysiological process of atopic diseases. Eosinophilic chronic rhinosinusitis with nasal polyps (eCRSwNP) is a local atopic disease of the systemic immune response. Alterations in the gut microbiome in eCRSwNP patients remain largely undefined.

METHODS

16S rRNA gene sequencing was performed in a cross-sectional study of 17 eCRSwNP patients, 9 noneCRSwNP patients and 13 healthy controls, and gut microbiota DNA sequencing between each pair of groups was compared using bioinformatic methods.

RESULTS

Compared with that of healthy controls, the gut microbiomes of eCRSwNP patients were characterised by a distinct overall microbial composition. However, no significant differences were found in the alpha diversity of the gut microbiota between patients and healthy controls. The distinct differences in microbial composition were significantly correlated with the severity of disease. At the genus level, the abundance of Faecalibacterium positively correlated with Lund-Mackay CT scores. Similarly, the abundance of Turicibacter positively correlated with the percentage of tissue eosinophils.

CONCLUSIONS

We found alterations in the gut microbiome in eCRSwNP patients, and the alterations in the gut microbiome were correlated with the severity of disease.

Integrative multiomics analysis reveals association of gut microbiota and its metabolites with susceptibility to keloids

Keloid scarring is a fibroproliferative disease of the skin, which can significantly impact one's quality of life through cosmetic concerns, physical discomfort (itchy; painful), restricted movement, and psychological distress. Owing to the poorly understood pathogenesis of keloids and their high recurrence rate, the efficacy of keloid treatment remains unsatisfactory, particularly in patients susceptible to multiple keloids. We conducted fecal metagenomic analyzes and both untargeted and targeted plasma metabolomics in patients with multiple keloids (MK, n = 56) and controls with normal scars (NS, n = 60); tissue-untargeted metabolomics (MK, n = 35; NS, n = 32), tissue-targeted metabolomics (MK, n = 41; NS, n = 36), and single-cell sequencing analyzes (GSE163973). Differences in the gut microbiota composition, plasma metabolites, and tissue metabolites were observed between the MK and NS groups; the core gut microbiota, Oxalobacter formigenes, Bacteroides plebeius, and Parabacteroides distasonis, were identified via the gut microbiome co-occurrence network. Single-cell data helped clarify the specific cells affected by plasma metabolites. An area under the curve analysis using a random forest model based on fecal metagenomics, plasma metabolomics, and tissue metabolomics revealed that gut bacteria, plasma, and tissue metabolites were effective in distinguishing between MK and NS groups. Decreased Bacteroides plebeius could lower uracil levels, altering systemic lipid metabolism, which may change the metabolic phenotype of secretory reticular fibroblasts in wounds, potentially leading to MK. These findings may open new avenues for understanding the multifactorial nature of keloid formation from the gut-skin axis and highlight the potential for novel therapeutic strategies targeting keloid lesions and the underlying systemic imbalances affected by the gut microbiome.

Heterologous Expression of the Antiviral Lectin Griffithsin in Probiotic Saccharomyces boulardii and In Vitro Characterization of Its Properties

In this study, the probiotic yeast Saccharomyces boulardii was engineered to secrete the antiviral lectin griffithsin. Twelve genetic tools with the griffithsin gene were cloned into the vector pSF-TEF1-URA3 and introduced into S. boulardii. In the recombinant strains, a 16.9 kDa band was detected using SDS-PAGE and further recognized by griffithsin antibody with Western blotting. S. boulardii strains FM, FT, HC, and HE with a high yield of griffithsin were acquired for property characterization in vitro. The four recombinant strains displayed a similar growth pattern to that of the control strains, while their morphological characteristics had changed according to scanning electron microscopy. In simulated gastrointestinal digestive fluids, the survival rates of S. boulardii FM, FT, and HC were significantly decreased (86.32 ± 1.49% to 95.36 ± 1.94%) compared with those of the control strains, with survival rates between 95.88 ± 0.00% and 98.74 ± 1.97%. The hydrophobicity of S. boulardii FM, the strain with the highest griffithsin production, was significantly increased to 21.89 ± 1.07%, and it exhibited a reduced auto-aggregation rate (57.64 ± 2.61%). Finally, Vero cells infected with porcine epidemic diarrhea virus (PEDV) were used to evaluate the strains' antiviral activity, and the rate at which S. boulardii FM inhibited PEDV reached 131.36 ± 1.06%, which was significantly higher than that of the control group.

Resolution of Chronic Inflammation, Restoration of Epigenetic Disturbances and Correction of Dysbiosis as an Adjunctive Approach to the Treatment of Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with multifactorial and unclear pathogenesis. Its development is characterized by two key elements: epigenetic dysregulation of molecular pathways involved in AD pathogenesis and disrupted skin and gut microbiota (dysbiosis) that jointly trigger and maintain chronic inflammation, a core AD characteristic. Current data suggest that failed inflammation resolution is the main pathogenic mechanism underlying AD development. Inflammation resolution is provided by specialized pro-resolving mediators (SPMs) derived from dietary polyunsaturated fatty acids acting through cognate receptors. SPM levels are reduced in AD patients. Administration of SPMs or their stable, small-molecule mimetics and receptor agonists, as well as supplementation with probiotics/prebiotics, demonstrate beneficial effects in AD animal models. Epidrugs, compounds capable of restoring disrupted epigenetic mechanisms associated with the disease, improve impaired skin barrier function in AD models. Based on these findings, we propose a novel, multilevel AD treatment strategy aimed at resolving chronic inflammation by application of SPM mimetics and receptor agonists, probiotics/prebiotics, and epi-drugs. This approach can be used in conjunction with current AD therapy, resulting in AD alleviation.

Immunoglobulin-coating patterns reveal altered humoral responses to gut bacteria in pediatric cow milk allergies

BACKGROUND

Pediatric cow milk allergies (CMA) can occur in immunoglobulin (Ig) E and non-IgE-mediated forms. Unlike IgE-mediated allergies, the mechanisms of disease pathogenesis in non-IgE-mediated food allergy and an association with microbiome has not been well established. Previous studies have identified the presence of altered humoral responses to gut bacteria in IgE mediated allergies. Here, we analyzed IgA, IgE and IgG responses to gut bacteria in subjects with either IgE or non-IgE mediated CMA to identify relative proportions of Ig-coated bacteria and characterize unique disease specific microbial signatures.

METHODS

Multi-parametric flow cytometry analysis was used to identify IgA, IgE and IgG responses to gut bacteria in CMA patients. Cell sorting of Ig coated gut bacteria was subsequently performed followed by high throughput 16S rRNA gene sequencing and specific patterns of humoral responses to gut bacteria assessed in each study group.

RESULTS

We identified significant alterations in IgA and IgG gut bacterial coating patterns in CMA subjects. Proportions of IgA-coated bacteria were decreased in IgE mediated CMA subjects without atopic dermatitis (ALL) and non-IgE mediated CMA subjects (ENP), compared to healthy controls (CON). In comparison, IgG-coated bacteria was significantly elevated in CMA subjects with atopic dermatitis (AD). Alpha and beta diversities displayed significant differences in IgA-, IgE-, and IgG-coated bacteria in AD and ENP groups. Significant differences in bacteria coated by IgA, IgE and IgG were detected at Phyla, Genus and Species levels and associated bacterial dysbiosis in IgE and non-IgE mediated allergies were identified. Linear discriminant analysis (LDA) effect size (LEFse) revealed unique disease associated bacterial signatures, including several pathogenic bacteria namely Bacteroides fragilis, Ruminococcus gnavus, Eubacterium dolichum, Fusobacterium, Clostridium neonatale and Robinsoniella peoriensis. Receiver operating characteristic curve analysis confirmed the efficiency of using the bacterial signatures identified as biomarkers for disease.

CONCLUSIONS

Altered IgA and IgG responses to gut bacteria were identified in CMA subjects. The disease-specific responses were associated with alterations in bacterial diversity and concomitant dysbiosis of Ig-coated bacteria in IgE-mediated and non-IgE-mediated CMA pediatric subjects. The identification of pathogenic bacteria uniquely associated with different classes of allergic disease indicates a role of these bacteria in driving disease-specific pathological phenotypes.

Interconnection of the Gut-Skin Axis in NC/Nga Mouse with Atopic Dermatitis: Effects of the Three Types of Bifidobacterium bifidum CBT-BF3 (Probiotics, Postbiotics, and Cytosine-Phosphate-Guanine Oligodeoxynucleotide) on T Cell Differentiation and Gut Microbiota

The gut microbiota is an immune system regulator in the gut-skin axis. Dysfunctional interactions between the gut microbiota and the gut immune system can lead to the development of skin diseases such as atopic dermatitis (AD). Probiotics and postbiotics positively affect the balance of the gut microbiota, immune regulation, protection against pathogens, and barrier integrity. This study investigated the effects of probiotic Bifidobacterium bifidum, postbiotic B. bifidum (heat-killed), and cytosine-phosphate-guanine oligodeoxynucleotide (CpG ODN) on the gut microbiota and T cell differentiation in NC/Nga mice induced with AD. 2,4-Dinitrochlorobenzene-induced AD mice had an increased SCORing atopic dermatitis-index and increased mRNA expression levels of Th2 and Th17 cell transcription factors and cytokines, and thymic stromal lymphopoietin (TSLP) cytokine in their mesenteric lymph nodes (mLNs; p<0.05). However, oral administration of the three types of B. bifidum (probiotics, postbiotics, CpG ODN) to AD mice decreased the mRNA expression levels of Th2 and Th17 cell transcription factors and cytokines as well as TSLP cytokine. They increased the mRNA expression levels of regulatory T (Treg) cell transcription factor and cytokine, galectin-9, and filaggrin genes (p<0.05). These effects were more noticeable in the mLNs than in the spleen. In addition, AD mice showed a decrease in Faecalibacterium prausnitzii, Roseburia spp., Leuconostoc citreum, Weissella cibaria, and Weissella koreensis (p<0.05). However, oral administration of the three types of B. bifidum increased Bacteroides spp., Bifidobacterium spp., F. prausnitzii, and Roseburia spp. (p<0.05).

Patho-immunological mechanisms of atopic dermatitis: The role of the three major human microbiomes

Atopic dermatitis (AD) is a genetically predisposed allergic inflammatory dermatosis with chronic, pruritic, and recurrent features. Patients with AD have dry and itchy skin, often accompanied by chronic eczematous lesions, allergic rhinitis, or asthma, which has a considerable impact on their daily lives. With advances in genome sequencing technology, it has been demonstrated that microorganisms are involved in this disease, and the microorganisms associated with AD are attracting considerable research attention. An increasing number of studies conducted in recent years have demonstrated that an imbalanced microbiome in AD patients has substantial impact on disease prognosis, and the causes are closely tied to various immune mechanisms. However, the involvement of microorganisms in the pathogenesis of AD remains poorly understood. In this paper, we review the advances in research on the immunological mechanisms of the skin microbiome, intestinal microbiome, and lung microbiome that are related to AD prognosis and immunotherapy protocols. It is hoped that this approach will lay the foundation for exploring the pathogenesis of and emerging treatments for AD.

Fecal microbiota transplantation against moderate-to-severe atopic dermatitis: A randomized, double-blind controlled explorer trial

BACKGROUND

Fecal microbiota transplantation (FMT) is a novel treatment for inflammatory diseases. Herein, we assess its safety, efficacy, and immunological impact in patients with moderate-to-severe atopic dermatitis (AD).

METHODS

In this randomized, double-blind, placebo-controlled clinical trial, we performed the efficacy and safety assessment of FMT for moderate-to-severe adult patients with AD. All patients received FMT or placebo once a week for 3 weeks, in addition to their standard background treatments. Patients underwent disease severity assessments at weeks 0, 1, 2, 4, 8, 12, and 16, and blood and fecal samples were collected for immunologic analysis and metagenomic shotgun sequencing, respectively. Safety was monitored throughout the trial.

RESULTS

Improvements in eczema area and severity index (EASI) scores and percentage of patients achieving EASI 50 (50% reduction in EASI score) were greater in patients treated with FMT than in placebo-treated patients. No serious adverse reactions occurred during the trial. FMT treatment decreased the Th2 and Th17 cell proportions among the peripheral blood mononuclear cells, and the levels of TNF-α, and total IgE in serum. By contrast, the expression levels of IL-12p70 and perforin on NK cells were increased. Moreover, FMT altered the abundance of species and functional pathways of the gut microbiota in the patients, especially the abundance of Megamonas funiformis and the pathway for 1,4-dihydroxy-6-naphthoate biosynthesis II.

CONCLUSION

FMT was a safe and effective therapy in moderate-to-severe adult patients with AD; the treatment changed the gut microbiota compositions and functions.

Nutritional and Microbial Strategies for Treating Acne, Alopecia, and Atopic Dermatitis

BACKGROUND/OBJECTIVES

Diet is one of the major determinants of the composition and function of the gut microbiome, and diverse studies have established directional connections between gut microbiome dysbiosis and skin dyshomeostasis. Furthermore, a significant link between the gut and certain skin-related disorders has been reported. This work reviews the mechanisms underlying the relationship between nutritional factors, gut microbiome, and certain skin diseases such as acne vulgaris, alopecia, and atopic dermatitis. In addition, it explores how the modulation of the gut microbiome and human skin through diet and various microbial strategies, including probiotics, synbiotics, postbiotics, and fecal microbiota transplantation, may serve as future treatments for skin diseases, possibly replacing traditional methods such as antibiotic, topical corticosteroid, and laser therapies.

RESULTS

The adequate intake of certain foods can promote a balanced gut microbiome, potentially reducing skin inflammation and improving overall skin health, while poor dietary choices may lead to worse outcomes by disrupting gut homeostasis. In this regard, diets high in antioxidants, fiber, and phytonutrients appear to be beneficial for enhancing skin health and preventing associated comorbidities. In addition, the administration of probiotics, synbiotics, and postbiotics in the treatment of cutaneous diseases has been shown to restore skin dyshomeostasis and to improve the symptoms of the reviewed skin conditions.

CONCLUSIONS

Consuming a healthy, plant-based diet can reduce skin inflammation and enhance overall skin health. Although the application of probiotics, synbiotics, and postbiotics has demonstrated promise in modulating inflammation, enhancing tissue regeneration, and inhibiting pathogenic colonization, further research is required.

Colorectal cancer-associated bacteria are broadly distributed in global microbiomes and drivers of precancerous change

The gut microbiome is implicated in the pathogenesis of colorectal cancer (CRC), but the full scope of this dialogue is unknown. Here we aimed to define the scale and membership of the body of CRC- and health-associated gut bacteria in global populations. We performed a microbiome-CRC correlation analysis of published ultra-deep shotgun metagenomic sequencing data from global microbiome surveys, utilizing a de novo (reference-agnostic) gene-level clustering approach to identify protein-coding co-abundant gene (CAGs) clusters. We link an unprecedented ~ 23-40% of gut bacteria to CRC or health, split nearly evenly as CRC- or health-associated. These microbes encode 2319 CAGs encompassing 427,261 bacterial genes significantly enriched or depleted in CRC. We identified many microbes that had not previously been linked to CRC, thus expanding the scope of "known unknowns" of CRC-associated microbes. We performed an agnostic CAG-based screen of bacterial isolates and validated predicted effects of previously unimplicated bacteria in preclinical models, in which we observed differential induction of precancerous adenomas and field effects. Single-cell RNA sequencing disclosed microbiome-induced senescence-associated gene expression signatures in discrete colonic populations including fibroblasts. In organoid co-cultures, primary colon fibroblasts from mice with microbiomes promoted significantly greater growth than fibroblasts from microbiome-depleted mice. These results offer proof-of-principle for gene-level metagenomic analysis enabling discovery of microbiome links to health and demonstrate that the microbiome can drive precancer states, thereby potentially revealing novel cancer prevention opportunities.

Structural Insights and Catalytic Mechanism of 3-Hydroxybutyryl-CoA Dehydrogenase from Faecalibacterium Prausnitzii A2-165

Atopic dermatitis (AD) is characterized by a T-helper cell type 2 (Th2) inflammatory response leading to skin damage with erythema and edema. Comparative fecal sample analysis has uncovered a strong correlation between AD and Faecalibacterium prausnitzii strain A2-165, specifically associated with butyrate production. Therefore, understanding the functional mechanisms of crucial enzymes in the butyrate pathway, such as 3-hydroxybutyryl-CoA dehydrogenase of A2-165 (A2HBD), is imperative. Here, we have successfully elucidated the three-dimensional structure of A2HBD in complex with acetoacetyl-CoA and NAD+ at a resolution of 2.2Å using the PAL-11C beamline (third generation). Additionally, X-ray data of A2HBD in complex with acetoacetyl-CoA at a resolution of 1.9 Å were collected at PAL-XFEL (fourth generation) utilizing Serial Femtosecond Crystallography (SFX). The monomeric structure of A2HBD consists of two domains, N-terminal and C-terminal, with cofactor binding occurring at the N-terminal domain, while the C-terminal domain facilitates dimerization. Our findings elucidate the binding mode of NAD+ to A2HBD. Upon acetoacetyl-CoA binding, the crystal structure revealed a significant conformational change in the Clamp-roof domain (root-mean-square deviation of 2.202 Å). Notably, residue R143 plays a critical role in capturing the adenine phosphate ring, underlining its significance in substrate recognition and catalytic activity. The binding mode of acetoacetyl-CoA was also clarified, indicating its lower stability compared to NAD+. Furthermore, the conformational change of hydrophobic residues near the catalytic cavity upon substrate binding resulted in cavity shrinkage from an open to closed conformation. This study confirms the conformational changes of catalytic triads involved in the catalytic reaction and presents a proposed mechanism for substrate reduction based on structural observations.

Changes in respiratory tract and gut microbiota in AR mice and their relationship with Th1/Th2/Treg

BACKGROUND

The etiology of allergic rhinitis (AR) is not fully understood. Studies have shown that the maturation of children's immune systems is closely related to microecology. However, few studies have focused simultaneously on changes in respiratory and gut microbiota in AR and their correlation between microecological changes and Th1/Th2/Treg.

OBJECTIVE

The aim is to investigate the pathogenesis of AR based on respiratory microecology, gut microecology, and Th1/Th2/Treg levels by applying microbiome techniques and correlation analysis.

METHODS

Standardized OVA-induced AR mice were established. Serum OVA-sIgE, IL-4, IFN-γ, IL-10 were measured by ELISA, Tregs in lymph nodes were determined by flow cytometry, and the histological characteristics of nasal tissues were evaluated by Hematoxylin & Eosin (H&E). Nasal symptoms were observed to determine the reliability of the AR mouse model. Nasal lavage fluid (NALF) and fecal samples were collected after the last OVA challenge. The composition of respiratory microbiota in NALF and gut microbial in feces samples via 16S rRNA gene sequencing between the two groups, further explored the relationship between microbiota and Th1/Th2/Treg levels.

RESULTS

In the AR group, the incidence of nose rubbing and sneezing in each mouse was significantly increased compared with the control group (all P < 0.001) and the inflammatory cell infiltration of NALF shows a significant increase in eosinophilic and neutrophilic infiltrates upon the AR group; H&E showed that the nasal mucosa of AR mice infiltration of massive eosinophils cells and neutrophils cells. OVA-sIgE and IL-4 in the AR group were increased (P < 0.01, P < 0.05) and IFN-γ, IL-10 were significantly decreased (P < 0.01, P < 0.05). Tregs showed a downward trend in the AR group, but there was no statistical difference. Compared with the control group, the respiratory microbiota of AR mice did not change significantly, while the gut microbiota changed significantly. In gut microbiota, compared to the control group, Shannon index in the AR group revealed a significant decrease at the genus level (P < 0.01), and Simpson index was significantly increased at all levels (all P < 0.05). PCoA also showed significant differences in beta diversity between the two groups (all P < 0.05). Compared to the control group, Deferribacteres at phylum level, Roseburia, Ruminiclostridium, Anaerotruncus at genus level were significantly decreased in the AR group (all P < 0.05). Spearman's rank correlation showed that OVA-sIgE was positively correlated with Bacteroidetes, Muribaculaceae and Erysipelotrichaceae (all P < 0.05); IL-4 was significantly negatively correlated with Epsilonbacteraeota and Deferribacteres (all P < 0.05). Treg was significantly positively correlated with Patescibacteria, Lachnospiraceae, and Saccharimonadaceae in gut microecology.

CONCLUSION

Our results showed that the respiratory microbiota of AR mice was not significantly altered, but the gut microbiota varied significantly and there was a correlation between gut microbiota and Th1/Th2/Treg.

Fecal microbiota transplantation for the treatment of chronic inflammatory skin diseases

The regulation of immune functions and the maintenance of homeostasis in the internal environment are both integral to human gut microbiota (GM). If GM is disturbed, it can result in a range of autoimmune diseases, including chronic inflammatory skin conditions. Chronic inflammatory skin diseases driven by T or B-cell-mediated immune reactions are complex, including the most prevalent diseases and some rare diseases. Expanding knowledge of GM dysbiosis in chronic inflammatory skin diseases has emerged. The GM has some causal roles in the pathogenesis of these skin conditions. Targeting microbiota treatment, particularly fecal microbiota transplantation (FMT), is considered to be a promising strategy. FMT was commonly used in intestinal diseases by reshaping and balancing GM, serving as a reasonable administration in these skin inflammatory diseases. This paper summarizes the existing knowledge of GM dysbiosis in chronic inflammatory skin diseases and the research data on FMT treatment for such conditions.

The human microbiome in space: parallels between Earth-based dysbiosis, implications for long-duration spaceflight, and possible mitigation strategies

SUMMARYThe human microbiota encompasses the diverse communities of microorganisms that reside in, on, and around various parts of the human body, such as the skin, nasal passages, and gastrointestinal tract. Although research is ongoing, it is well established that the microbiota exert a substantial influence on the body through the production and modification of metabolites and small molecules. Disruptions in the composition of the microbiota-dysbiosis-have also been linked to various negative health outcomes. As humans embark upon longer-duration space missions, it is important to understand how the conditions of space travel impact the microbiota and, consequently, astronaut health. This article will first characterize the main taxa of the human gut microbiota and their associated metabolites, before discussing potential dysbiosis and negative health consequences. It will also detail the microbial changes observed in astronauts during spaceflight, focusing on gut microbiota composition and pathogenic virulence and survival. Analysis will then turn to how astronaut health may be protected from adverse microbial changes via diet, exercise, and antibiotics before concluding with a discussion of the microbiota of spacecraft and microbial culturing methods in space. The implications of this review are critical, particularly with NASA's ongoing implementation of the Moon to Mars Architecture, which will include weeks or months of living in space and new habitats.

Antibacterial and Antiallergic Effects of Three Tea Extracts on Histamine-Induced Dermatitis

Atopic dermatitis (AD) is a persistent and recurrent inflammatory skin condition with a genetic basis. However, the fundamental reasons and mechanisms behind this phenomenon remain incompletely understood. While tea extracts are known to reduce histamine-induced skin allergies and inflammation, the specific mechanisms by which various types of Chinese tea provide their protective effects are still not fully elucidated. In this study, a model of skin itching induced by histamine is used to explore the functions and mechanisms of three types of tea extract (Keemun black tea (HC), Hangzhou green tea (LC), and Fujian white tea (BC)) in alleviating histamine-induced dermatitis. The components of three tea extracts are identified by UPLC-Q-TOF-MS, and we found that their main components are alkaloids, fatty acyls, flavonoids, organic acids, and phenols. The inhibitory effects of three types of tea extract on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in skin injury are investigated by MIC and flow cytometry. The three types of tea extract have an inhibitory effect on the growth of bacterial flora, with HC showing the best inhibitory activity. The effect of the three types of tea extract on histamine-induced dermatitis is also evaluated. Furthermore, itchy skin experiments, HE staining, toluidine blue staining, and immunohistochemical staining of mouse skin tissues were performed to determine the variations of scratching, epidermal thickness, mast cell number, IL-1β, and NGF content after the administration of the tea extracts. The three types of tea extracts all alleviate and inhibit skin itching, epidermal hyperplasia, and allergic dermatitis. BC effectively alleviates epidermal hyperplasia caused by skin allergies, and LC significantly downregulates NGF. HC reduces histamine-induced mast cell infiltration and downregulates IL-1β to alleviate skin itching. Consequently, tea emerges a potent natural product that can inhibit the growth of skin wound bacterial flora and exhibit skin repair effects on histamine-induced allergic dermatitis.

Mapping the relationship between atopic dermatitis and gut microbiota: a bibliometric analysis, 2014-2023

Background

Atopic dermatitis (AD) is a chronic inflammatory skin condition affecting a significant portion of the population, with prevalence rates of 25% in children and 7-10% in adults. AD not only poses physical challenges but also profoundly impacts patients' mental well-being and quality of life. The stability of gut microbiota is crucial for overall health and can influence AD progression by modulating immune function, skin barrier integrity, and neuroendocrine signaling, which may be an effective target for the prevention and treatment of AD. Thus, exploring the interactions between AD and gut microbiota, particularly in infants, can provide insights into potential preventive and therapeutic strategies. This study aimed to explore the correlation between AD and gut microbiota while providing an overview of current research trends and emerging areas of interest in this field.

Methods

A comprehensive search was conducted on the Web of Science Core Collection (WOSCC) for relevant publications from January 1, 2014, to December 31, 2023. English-language articles and reviews were included. Two investigators independently screened the publications, and visual analysis was performed using CiteSpace, VOSviewer, Scimago Graphica, and Microsoft Excel software.

Results

A total of 804 articles were included, showing a significant increase in publications over the past decade. The United States, Wageningen University, and University Ulsan (represented by Hong SJ) had the highest number of published papers. Nutrients was the journal with the most publications, while the Journal of Allergy and Clinical Immunology had the highest number of citations and centrality among co-cited journals. Keyword visualization analysis identified "atopic dermatitis" and "gut microbiota" as central themes. Notably, there has been a notable shift in research focus over the years, with early studies concentrating on "Fecal microbiota," "caesarean section," and "first 6 months," while recent studies have highlighted the roles of "cells," "dysbiosis," and "prebiotics." This shift indicates growing interest in the underlying mechanisms and potential therapeutic interventions related to the intestinal microecology in AD treatment.

Conclusion

The field of AD and gut microbiota research has evolved significantly, with an increasing focus on understanding the intricate interactions between gut microbiota and AD pathogenesis. Recent years have witnessed increased interest in understanding the relationship between AD and gut microbiota, with researchers conducting extensive studies exploring various aspects of this connection. This review analyzes research trends over the past decade, highlighting trends and hotspots in the study of AD, particularly in infants, and the role of microbiota. This review serves as a valuable reference for future investigations, aiming to provide deeper insights into this burgeoning field and suggests directions for future research.

Next generation probiotics for human health: An emerging perspective

Over recent years, the scientific community has acknowledged the crucial role of certain microbial strains inhabiting the intestinal ecosystem in promoting human health, and participating in various beneficial functions for the host. These microorganisms are now referred to as next-generation probiotics and are currently considered as biotherapeutic products and food or nutraceutical supplements. However, the majority of next-generation probiotic candidates pose nutritional demands and exhibit high sensitivity towards aerobic conditions, leading to numerous technological hurdles in large-scale production. This underscores the need for the development of suitable delivery systems capable of enhancing the viability and functionality of these probiotic strains. Currently, potential candidates for next generation probiotics (NGP) are being sought among gut bacteria linked to health, which include strains from the genera Bacteroids, Faecalibacterium, Akkermansia and Clostridium. In contrast to Lactobacillus spp. and Bifidobacterium spp., NGP, particularly Bacteroids spp. and Clostridium spp., appear to exhibit greater ambiguity regarding their potential to induce infectious diseases. The present review provides a comprehensive overview of NGPs in terms of their health beneficial effects, regulation framework and risk assessment targeting relevant criteria for commercialization in food and pharmaceutical markets.

The Skin Histopathology of Pro- and Parabiotics in a Mouse Model of Atopic Dermatitis

As it has been revealed that the activation of human immune cells through the activity of intestinal microorganisms such as pro- and prebiotics plays a vital role, controlling the proliferation of beneficial bacteria and suppressing harmful bacteria in the intestine has become essential. The importance of probiotics, especially for skin health and the immune system, has led to the emergence of products in various forms, including probiotics, prebiotics, and parabiotics. In particular, atopic dermatitis (AD) produces hypersensitive immunosuppressive substances by promoting the differentiation and activity of immune regulatory T cells. As a result, it has been in the Th1 and Th2 immune balance through a mechanism that suppresses skin inflammation or allergic immune responses caused by bacteria. Furthermore, an immune mechanism has recently emerged that simultaneously controls the expression of IL-17 produced by Th17. Therefore, the anti-atopic effect was investigated by administering doses of anti-atopic candidate substances (Lactobacilus sakei CVL-001, Lactobacilus casei MCL, and Lactobacilus sakei CVL-001 Lactobacilus casei MCL mixed at a ratio of 4:3) in an atopy model using 2,4-dinitrochlorobenzene and observing symptom changes for 2 weeks to confirm the effect of pro-, para-, and mixed biotics on AD. First, the body weight and feed intake of the experimental animals were investigated, and total IgG and IgM were confirmed through blood biochemical tests. Afterward, histopathological staining was performed using H&E staining, Toluidine blue staining, Filaggrin staining, and CD8 antibody staining. In the treatment group, the hyperproliferation of the epidermal layer, the inflammatory cell infiltration of the dermal layer, the expression of CD8, the expression of filaggrin, and the secretion of mast cells were confirmed to be significantly reduced. Lastly, small intestine villi were observed through a scanning microscope, and scoring evaluation was performed through skin damage. Through these results, it was confirmed that AD was reduced when treated with pro-, para-, and mixed biotics containing probiotics and parabiotics.

Probiotics suppress LL37 generated rosacea-like skin inflammation by modulating the TLR2/MyD88/NF-κB signaling pathway

Rosacea, a chronic inflammatory dermatological condition, is characterized by facial erythema and pustules. Recent investigations have delved into the interplay between the gut microbiota and rosacea pathogenesis, unveiling promising avenues for therapeutic intervention. In this study, we screened and isolated strains Ligilactobacillus salivarius 23-006 and Lacticaseibacillus paracasei 23-008 from the feces of healthy volunteers and evaluated the intervention effects of probiotics on rosacea by constructing an LL37 induced rosacea-like mouse model. Our results showed that both L. salivarius 23-006 and L. paracasei 23-008 were probiotic strains with favourable properties. In specific, we observed that both L. salivarius 23-006 and L. paracasei 23-008 alleviated skin lesions, reduced skin inflammatory infiltrates, and decreased the expression of inflammatory factors in mice, with the combination of L. salivarius 23-006 and L. paracasei 23-008 having the most significant effect. Moreover, the combination of strains reduced the expression of cathelicidin LL37 and rosacea-associated factors by inhibiting the TLR2/MyD88/NF-κB pathway. The 16S rRNA analysis showed that the combination enhanced the intestinal barrier, restored intestinal microbiota homeostasis, and up-regulated the abundance of Lactobacillus while down-regulating the abundance of Coprococcus and Oscillospira. We also explored the effects of postbiotics of L. salivarius 23-006 and L. paracasei 23-008 on rosacea. While postbiotics could also ameliorate the rosacea-like phenotype in mice via the TLR2/MyD88/NF-κB pathway, the effects were not as pronounced as those observed with probiotic treatment. However, the postbiotics still enhanced the intestinal barrier, up-regulated the Lactobacillus abundance, and modulated the intestinal microbiota. In conclusion, our study revealed that L. salivarius 23-006 and L. paracasei 23-008 improved rosacea by regulating the TLR2/MyD88/NF-κB pathway and intestinal microbiota, providing a theoretical basis for the treatment of rosacea.

Time-dependent risk of atopic dermatitis following nontyphoidal Salmonella infection

BACKGROUND

The pathogenesis of atopic dermatitis (AD) remains unclear. Nontyphoidal Salmonella (NTS) infection might trigger immune-mediated reactions. We aimed to examine NTS and the risk of subsequent AD.

METHODS

From 2002 to 2015, eligible patients (aged 0-100 years) with NTS were identified. NTS and non-NTS groups were matched at a 1:10 ratio on age and sex. We utilized conditional multivariable Cox proportional hazard models to estimate the adjusted hazard ratio (aHR) and 95% confidence interval (CI) for AD development. Subgroup analyses were conducted based on age, sex, and severity of NTS infection. We utilized landmark analysis to explore the time-dependent hazard of AD following NTS.

RESULTS

In the NTS group (N = 6624), 403 developed AD. After full adjustment of demographics and comorbidities, the NTS group had a higher risk of AD than the reference group (aHR = 1.217, 95% CI = 1.096-1.352). Age-stratified analysis revealed that NTS group exhibited an elevated risk compared to the reference group, particularly among those aged 13-30 years (aHR = 1.25, 95% CI = 1.017-1.559), individuals aged 31-50 years (aHR = 1.388, 95% CI = 1.112-1.733), those aged 51-70 years (aHR = 1.301, 95% CI = 1.008-1.679), and individuals aged 71 years and over (aHR = 1.791, 95% CI = 1.260-2.545). Severe NTS was associated with a higher risk of AD than the reference group (aHR = 2.411, 95% CI = 1.577-3.685). Landmark analysis showed generally consistent findings.

CONCLUSIONS

Minimizing exposure to NTS infection may represent a prospective strategy for averting the onset and progression of atopic dermatitis.

Short-chain fatty acids: linking diet, the microbiome and immunity

The short-chain fatty acids (SCFAs) butyrate, propionate and acetate are microbial metabolites and their availability in the gut and other organs is determined by environmental factors, such as diet and use of antibiotics, that shape the diversity and metabolism of the microbiota. SCFAs regulate epithelial barrier function as well as mucosal and systemic immunity via evolutionary conserved processes that involve G protein-coupled receptor signalling or histone deacetylase activity. Indicatively, the anti-inflammatory role of butyrate is mediated through direct effects on the differentiation of intestinal epithelial cells, phagocytes, B cells and plasma cells, and regulatory and effector T cells. Intestinally derived SCFAs also directly and indirectly affect immunity at extra-intestinal sites, such as the liver, the lungs, the reproductive tract and the brain, and have been implicated in a range of disorders, including infections, intestinal inflammation, autoimmunity, food allergies, asthma and responses to cancer therapies. An ecological understanding of microbial communities and their interrelated metabolic states, as well as the engineering of butyrogenic bacteria may support SCFA-focused interventions for the prevention and treatment of immune-mediated diseases.

Characteristics of gut microbiota and serum metabolism in patients with atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease that affects 15%-30% of children and 10% of adults globally, with its incidence being influenced by genetic, environmental, and various other factors. While the immune plays a crucial role in the development, the composition of gut microbiota and serum metabolites also contribute to its pathogenesis.

SUBJECT

Study the characteristics of gut microbiota and serum metabolites in patients with atopic dermatitis METHOD: In this study, we collected stool and serum samples from 28 AD patients and 23 healthy individuals (NC) for metagenomic sequencing of gut microbiota and non-targeted metabolomic sequencing of serum.

RESULT

Our results revealed a lower diversity of gut microbiota in the AD group compared to the NC group. The predominant Phylum in AD patients were Bacteroidetes, Pseudomonas, and Verrucomicrobia, with the most dominant bacterial genus being Faecalibacterium. At the species level, Prevotella copri and Faecalibacterium prausnitzii were found to be the most abundant bacteria. Significant differences in serum metabolite profiles were observed between NC and AD patients, with noticeable variations in metabolite expression levels. The majority of metabolites in the serum of AD patients exhibited low expression, while a few showed high expression levels. Notably, metabolites such as Cholesterol glucuronide, Styrene, Lutein, Betaine, Phosphorylcholine, Taurine, and Creatinine displayed the most pronounced alterations.

CONCLUSION

These findings contribute to a further understanding of the complexities underlying this disease.

Systematic review of the association between short-chain fatty acids and allergic diseases

We performed a systematic review to investigate the current evidence on the association between allergic diseases and short chain fatty acids (SCFAs), which are microbially produced and suggested as one mechanism on how gut microbiome affects the risk of allergic diseases. Medline, Embase and Web of Science were searched from data inception until September 2022. We identified 37 papers, of which 17 investigated prenatal or early childhood SCFAs and the development of allergic diseases in childhood, and 20 assessed SCFAs in patients with pre-existing allergic diseases. Study design, study populations, outcome definition, analysis method and reporting of the results varied between papers. Overall, there was some evidence showing that the three main SCFAs (acetate, propionate and butyrate) in the first few years of life had a protective effect against allergic diseases, especially for atopic dermatitis, wheeze or asthma and IgE-mediated food allergy in childhood. The association between each SCFA and allergic disease appeared to be different by disease and the age of assessment. Further research that can determine the potentially timing specific effect of each SCFA will be useful to investigate how SCFAs can be used in treatment or in prevention against allergic diseases.

Sucrose Solution Ingestion Exacerbates Dinitrofluorobenzene-Induced Allergic Contact Dermatitis in Rats

Allergic dermatitis is a skin disease with growing prevalence worldwide that has been associated with diets high in fats and sugars. Regular consumption of sucrose-containing beverages may increase the risk for several health problems, including allergic diseases and particularly asthma, but the association between sucrose consumption and allergic dermatitis is understudied. We investigated the effects of sucrose solution intake on allergic contact dermatitis in rats and found early exacerbation of 2,4-dinitrofluorobenzene (DNFB)-induced disease symptoms and altered composition of the gut microbiota after 14 d of intake. The levels of short-chain fatty acids-produced by fermentation by the intestinal microbiota-were not affected in the cecal contents and feces but decreased in the blood; this effect was especially notable for acetate. To restore blood acetate concentrations, triacetin was mixed with a 10% sucrose solution and fed to the rat model. This strategy prevented the early exacerbation of DNFB-induced symptoms. The decreased absorption of short-chain fatty acids from the intestinal lumen was not linked to the decreased expression of short-chain fatty acid transporters in the small intestine; instead, the mechanism involves a reduction in the sodium concentration in the intestinal lumen due to increased expression of sodium-glucose transporter 1 (SGLT1).

The Association between Migration and Prevalence of Allergic Diseases: A Systematic Review and Meta-Analysis

INTRODUCTION

Allergic diseases remain of concern due to their increasing prevalence worldwide. Intrinsic and environmental risk factors have been implicated in the pathogenesis of allergic disease. Among the possible risk factors, migration has been associated with the manifestation of allergic diseases. We aimed to consolidate the existing evidence, review the hypotheses for the relationship between environmental factors and allergic disease, and provide a direction for future work.

METHODS

This systematic review and meta-analysis complied with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The Web of Science database was searched in September 2023 to retrieve publications investigating the relationship between allergic rhinitis (AR), atopic dermatitis (AD), or asthma and the following factors: (i) migrant status (i.e., migrants vs. natives) or (ii) duration since migration among migrants. Risk of bias was assessed using the JBI critical appraisal tool. Details and findings from the included studies were also summarized and meta-analyses were conducted where appropriate.

RESULTS

Fifty studies encompassing an estimated 3,755,248 individuals were reviewed. Articles investigated asthma (n = 46), AR (n = 16), and AD (n = 14). A variety of migration-related factors were also studied: movement of individuals across regions (n = 40), duration since immigration (n = 12), age at immigration (n = 9), and acculturation (n = 2). Migration status was not significantly associated with AD (pooled odds ratio [pOR] = 0.68, 95% confidence interval (CI) = 0.31, 1.49). Although AR prevalence was lower among immigrants than natives (pOR = 0.58, 95% CI = 0.45, 0.74), immigrants who had resided at least 10 years in the destination country had a higher risk of AR than immigrants with a duration of residence of less than 10 years (pOR = 8.36, 95% CI = 4.15, 16.81). Being an immigrant was also associated with a decreased risk of asthma (pOR = 0.56, 95% CI = 0.44, 0.72). Among immigrants, residing in the host country for at least 10 years was associated with increased asthma manifestation (pOR = 1.85, 95% CI = 1.25, 2.73). Immigrants who migrated aged 5 and below did not exhibit a significantly higher likelihood of asthma than migrants who immigrated older than 5 years (pOR = 1.01, 95% CI = 0.68, 1.50).

CONCLUSION

This review was limited by the primarily cross-sectional nature of the included studies. Objective diagnoses of allergic disease, such as using the spirometry of bronchodilator reversibility test for asthma rather than questionnaire responses, could add to the reliability of the outcomes. Furthermore, immigrant groups were mostly nonspecific, with little distinction between their country of origin. Overall, migration appears to be a protective factor for allergic diseases, but the protection subsides over time and the prevalence of allergic diseases among the immigrant group approaches that of the host population.

The Role of the Microbiota in the Pathogenesis and Treatment of Atopic Dermatitis-A Literature Review

Atopic dermatitis (AD) is a chronic inflammatory skin condition with a high prevalence worldwide. AD pathogenesis is complex and consists of immune system dysregulation and impaired skin barrier, influenced by genetic and environmental factors. The purpose of the review is to show the complex interplay between atopic dermatitis and the microbiota. Human microbiota plays an important role in AD pathogenesis and the course of the disease. Dysbiosis is an important factor contributing to the development of atopic diseases, including atopic dermatitis. The gut microbiota can influence the composition of the skin microbiota, strengthening the skin barrier and regulating the immune response via the involvement of bacterial metabolites, particularly short-chain fatty acids, in signaling pathways of the gut-skin axis. AD can be modulated by antibiotic intake, dietary adjustments, hygiene, and living conditions. One of the promising strategies for modulating the course of AD is probiotics. This review offers a summary of how the microbiota influences the development and treatment of AD, highlighting aspects that warrant additional investigation.

Hand Sanitizer: Stopping the Spread of Infection at a Cost

The recent rise in hand sanitizer use due to the COVID-19 pandemic has had a beneficial impact on stopping the spread of disease, but the potential negative implications of its overuse on the body and the microbiome have yet to be thoroughly reviewed. Epidermal layers absorb hand sanitizer from direct application to the skin, making them some of the most susceptible cells to the adverse effects of overuse. The increased usage of hand sanitizer can affect the variation, quantity, and diversity of the skin microflora, leading to conditions such as eczema, atopic dermatitis, and even systemic toxicity due to colonization of the skin with pathogenic bacteria. Due to the close-knit relationship between the skin and gut, the gastrointestinal system can also incur disruptions due to the negative effects on the skin as a result of excessive hand sanitizer use, leading to gut dysbiosis. Additionally, the accidental ingestion of hand sanitizer, and its abuse or misuse, can be toxic and lead to alcohol poisoning, which is an issue most commonly seen not only in the pediatric population but also in adolescents and adults due to aberrant recreational exposure. As a vulnerable body system, the eyes can also be negatively impacted by hand sanitizer misuse leading to chemical injury, visual impairment, and even blindness. In this review, we aim to highlight the variations in hand sanitizer formulation, the benefits, and how misuse or overuse may lead to adverse effects on the skin, gut, and eyes. In particular, we review the advantages and disadvantages of alcohol-based hand sanitizers (ABHSs) and non-alcohol-based hand sanitizers (NABHSs) and how the components and chemicals used in each can contribute to organ dysbiosis and systemic damage.

Specific vaginal and gut microbiome and the anti-tumor effect of butyrate in cervical cancer women

OBJECTIVE

To investigate the vaginal and gut microbes changes during the carcinogenesis of cervical and the auxiliary diagnostic value. To investigate the effect of microbiome-specific metabolites butyric on cervical cancer cells.

METHODS

We studied 416 vaginal 16S rRNA sequencing data and 116 gut sequencing data. Reads were processed using VSEARCH. We used Shannon index, Chao1 index, Simpson diversity index, β diversity index, Linear discriminant analysis Effect Size (LEfSe), co-abundance network and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis to explore microbiome differences between groups. We constructed random forest models based on genus and verified its discriminant effect. Finally, we used the cell counting kit-8 (CCK-8) method to detect cell proliferation capacity and flow cytometry to detect apoptosis and induction of cell cycle progression.

RESULTS

Compared to the non-cancerous population, patients with cervical cancer had unique microbial community characteristics in both vaginal and gut ecological niches. Our predictive model based on genus in two ecological regions achieved high accuracy in the diagnosis of cervical cancer (vaginal model AUC=91.58 %; gut model AUC=99.95 %). Butyric inhibited cervical cancer cell proliferation in a concentration-dependent manner and promoted apoptosis of cancer cells.

CONCLUSION

Significant differences were found in vaginal and gut microbes in patients with cervical cancer compared to the non-cancerous population. The prediction models constructed at the genus level in both ecological sites have good diagnostic value. Microorganisms may be involved in cervical cancer progression in a metabolite-dependent way, and targeting butyric may provide therapeutic options for cervical cancer.

Atopic Dermatitis and Psoriasis: Similarities and Differences in Metabolism and Microbiome

Atopic dermatitis and psoriasis are common chronic inflammatory diseases of high incidence that share some clinical features, including symptoms of pruritus and pain, scaly lesions, and histologically, acanthosis and hyperkeratosis. Meanwhile, they are both commonly comorbid with metabolic disorders such as obesity and diabetes, indicating that both diseases may exist with significant metabolic disturbances. Metabolomics reveals that both atopic dermatitis and psoriasis have abnormalities in a variety of metabolites, including lipids, amino acids, and glucose. Meanwhile, recent studies have highlighted the importance of the microbiome and its metabolites in the pathogenesis of atopic dermatitis and psoriasis. Metabolic alterations and microbiome dysbiosis can also affect the immune, inflammatory, and epidermal barrier, thereby influencing the development of atopic dermatitis and psoriasis. Focusing on the metabolic and microbiome levels, this review is devoted to elaborating the similarities and differences between atopic dermatitis and psoriasis, thus providing insights into the intricate relationship between both conditions.

A non-inferiority clinical trial comparing probiotics and oral corticosteroids for the management of acute exacerbation of atopic dermatitis patients

A prospective controlled pilot study on the feasibility of utilization of a probiotic mixture for management of acute exacerbation of atopic dermatitis (AD). Patients were allocated to either standard of care (SOC) therapy with tapering dose of steroids or a probiotic mixture over 3 weeks. After the 3-week intervention, patients on steroids achieved significantly higher clinical response rates and significantly deeper response as measured by the change in SCORAD score. No gut microbiome changes could be appreciated in either group after the treatment period. We could conclude that probiotics cannot replace SOC therapy for the management of acute exacerbation of AD.

Efficacy and safety of purslane (Portulaca oleracea) for mild to moderate chronic hand eczema; A randomized, double-blind, placebo-controlled clinical trial

INTRODUCTION

Chronic hand eczema (CHE) is a common skin inflammation with a complex pathophysiology. Due to its anti-inflammatory properties, Portulaca oleracea L. (purslane) is traditionally used in Persian medicine for skin ailments. This study aimed to evaluate the safety and efficacy of a standardized purslane extract (based on traditional Persian medicine) for adults with mild or moderately severe CHE.

METHODS

A randomized, double-blind, placebo-controlled clinical trial was conducted at Razi Hospital in Iran from January to June 2022. Participants were randomly allocated to receive an oral purslane or placebo syrup plus topical Vaseline for four weeks. Seventy participants were randomly allocated into the intervention (n = 35) and placebo (n = 35) groups. The primary outcomes were the extent and severity of CHE symptoms over the four weeks after adjusting for age, gender and baseline score. Secondary outcomes were quality of life, symptom recurrence, treatment satisfaction, and adverse events.

RESULTS

After 4 weeks of treatment, compared to the placebo group (n = 31), the purslane group (n = 31) had significantly lower physician-reported fissure scores (adjusted mean difference (adjMD): -0.50, 95 %CI -3.93 to -0.34, p = 0.043), participant-reported itching (adjMD -0.51, 95 %CI -2.32 to -0.31, p = 0.041), dryness (adjMD -1.46, 95 %CI -2.89 to -0.03, p = 0.045), and total itching, dryness and thickness (adjMD -2.36, 95 %CI -6.23 to -1.51, p = 0.023) scores. Fourteen participants (purslane n = 10; placebo n = 4, p = 0.068) experienced adverse events of mild to moderate severity.

CONCLUSION

Purslane has some promising effects for reducing the extent and severity of CHE symptoms, and no direct comparisons have been made with commonly used treatments. Future multicenter trials and mechanistic studies are warranted to establish the safety and effectiveness of purslane as a potential therapeutic agent for CHE.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials (IRCT20200707048040N1).

Inflammatory bowel disease and allergic diseases: A Mendelian randomization study

BACKGROUND

Inflammatory bowel disease (IBD) and allergic diseases possess similar genetic backgrounds and pathogenesis. Observational studies have shown a correlation, but the exact direction of cause and effect remains unclear. The aim of this Mendelian randomization (MR) study is to assess bidirectional causality between inflammatory bowel disease and allergic diseases.

METHOD

We comprehensively analyzed the causal relationship between inflammatory bowel disease (IBD), Crohn's disease (CD), ulcerative colitis (UC) and allergic disease (asthma, Hay fever, and eczema) as a whole, allergic conjunctivitis (AC), atopic dermatitis (AD), allergic asthma (AAS), and allergic rhinitis (AR) by performing a bidirectional Mendelian randomization study using summary-level data from genome-wide association studies. The analysis results mainly came from the random-effects model of inverse variance weighted (IVW-RE). In addition, multivariate Mendelian randomization (MVMR) analysis was conducted to adjust the effect of body mass index (BMI) on the instrumental variables.

RESULTS

The IVW-RE method revealed that IBD genetically increased the risk of allergic disease as a whole (OR = 1.03, 95% CI = 1.01-1.04, fdr.p = .015), AC (OR = 1.04, 95% CI = 1.01-1.06, fdr.p = .011), and AD (OR = 1.06, 95% CI = 1.02-1.09, fdr.p = .004). Subgroup analysis further confirmed that CD increased the risk of allergic disease as a whole (OR = 1.02, 95% CI = 1.00-1.03, fdr.p = .031), AC (OR = 1.03, 95% CI = 1.01-1.05, fdr.p = .012), AD (OR = 1.06, 95% CI = 1.02-1.09, fdr.p = 2E-05), AAS (OR = 1.05, 95% CI = 1.02-1.08, fdr.p = .002) and AR (OR = 1.03, 95% CI = 1.00-1.07, fdr.p = .025), UC increased the risk of AAS (OR = 1.02, 95% CI = 0.98-1.07, fdr.p = .038). MVMR results showed that after taking BMI as secondary exposure, the causal effects of IBD on AC, IBD on AD, CD on allergic disease as a whole, CD on AC, CD on AD, CD on AAS, and CD on AR were still statistically significant. No significant association was observed in the reverse MR analysis.

CONCLUSION

This Mendelian randomized study demonstrated that IBD is a risk factor for allergic diseases, which is largely attributed to its subtype CD increasing the risk of AC, AD, ASS, and AR. Further investigations are needed to explore the causal relationship between allergic diseases and IBD.

Characteristics of Gut Microbiota in Rosacea Patients-A Cross-Sectional, Controlled Pilot Study

BACKGROUND

Recent studies have suggested a possible connection between rosacea and patients' gut microbiota.

OBJECTIVE

To investigate the differences in fecal microbial profiles between patients with rosacea and healthy controls.

METHODS

Gut microbiota of 54 rosacea patients (RP) were analyzed using MiSeq 16S rRNA sequencing. Enterotypes, the Firmicutes/Bacteroides (F/B) ratio, the significance of alpha and beta diversity, and differential abundance analysis (DAA) were calculated and compared with age- and gender-matched controls (CP, n = 50).

RESULTS

Significant changes in the enterotypes and F/B ratio were observed between the RP and CP (p = 0.017 and p = 0.002, respectively). The RP showed a decreased microbial richness and diversity compared to the CP (Shannon p = 0.012, inverse Simpson p = 0.034). Beta diversity also differed between both groups (PERMANOVA, p = 0.006). Fourteen significantly different taxa were detected according to DAA. Faecalibacterium prausnitzii (coef. -0.0800, p = 0.008), Lachnoospiraceae ND 3007 group sp. (coef. -0.073, p < 0.001), and Ruminococcaceae (coef. -0.072, p = 0.015) were significantly decreased; Oscillobacter sp. (coef. 0.023, p = 0.031), Flavonifractor plautii (coef. 0.011, p = 0.037), and Ruminococccaceae UBA 1819 (coef. 0.010, p = 0.031) were significantly increased in the RP compared to the CP.

CONCLUSION

Significant alterations in gut microbiota were present in the RP. Taxonomic shifts and reduced richness and diversity were observed when compared to the CP. Larger prospective studies are needed to investigate correlations with clinical features and to translate these findings into future therapeutic approaches.

Microbial perspective on the skin-gut axis and atopic dermatitis

Atopic dermatitis (AD) is a relapsing inflammatory skin condition that has become a global health issue with complex etiology and mounting prevalence. The association of AD with skin and gut microbiota has been revealed by virtue of the continuous development of sequencing technology and genomics analysis. Also, the gut-brain-skin axis and its mutual crosstalk mechanisms have been gradually verified. Accordingly, the microbiota-skin-gut axis also plays an important role in allergic skin inflammation. Herein, we reviewed the relationship between the microbiota-skin-gut axis and AD, explored the underlying signaling molecules and potential pathways, and focused on the potential mechanisms of probiotics, antimicrobial peptides (AMPs), coagulase-negative staphylococci transplantation, fecal microbiota transplantation, AMPs, and addition of essential fatty acids in alleviating AD, with the aim to provide a new perspective for targeting microbiota in the treatment of allergic skin inflammation.

Dermal injury drives a skin to gut axis that disrupts the intestinal microbiome and intestinal immune homeostasis in mice

The composition of the microbial community in the intestine may influence the functions of distant organs such as the brain, lung, and skin. These microbes can promote disease or have beneficial functions, leading to the hypothesis that microbes in the gut explain the co-occurrence of intestinal and skin diseases. Here, we show that the reverse can occur, and that skin directly alters the gut microbiome. Disruption of the dermis by skin wounding or the digestion of dermal hyaluronan results in increased expression in the colon of the host defense genes Reg3 and Muc2, and skin wounding changes the composition and behavior of intestinal bacteria. Enhanced expression Reg3 and Muc2 is induced in vitro by exposure to hyaluronan released by these skin interventions. The change in the colon microbiome after skin wounding is functionally important as these bacteria penetrate the intestinal epithelium and enhance colitis from dextran sodium sulfate (DSS) as seen by the ability to rescue skin associated DSS colitis with oral antibiotics, in germ-free mice, and fecal microbiome transplantation to unwounded mice from mice with skin wounds. These observations provide direct evidence of a skin-gut axis by demonstrating that damage to the skin disrupts homeostasis in intestinal host defense and alters the gut microbiome.