Impairment of skin barrier function via cholinergic signal transduction in a dextran sulphate sodium-induced colitis mouse model

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.

Atopic dermatitis: Pathophysiology, microbiota, and metabolome - A comprehensive review

Atopic dermatitis (AD) is a prevalent inflammatory skin condition that commonly occurs in children. Genetics, environment, and defects in the skin barrier are only a few of the factors that influence how the disease develops. As human microbiota research has advanced, more scientific evidence has shown the critical involvement of the gut and skin bacteria in the pathogenesis of atopic dermatitis. Microbiome dysbiosis, defined by changed diversity and composition, as well as the development of pathobionts, has been identified as a potential cause for recurring episodes of atopic dermatitis. Gut dysbiosis causes "leaky gut syndrome" by disrupting the epithelial lining of the gut, which allows bacteria and other endotoxins to enter the bloodstream and cause inflammation. The same is true for the disruption of cutaneous homeostasis caused by skin dysbiosis, which enables bacteria and other pathogens to reach deeper skin layers or even systemic circulation, resulting in inflammation. Furthermore, it is now recognized that the gut and skin microbiota releases both beneficial and toxic metabolites. Here, this review covers a range of topics related to AD, including its pathophysiology, the microbiota-AD connection, commonly used treatments, and the significance of metabolomics in AD prevention, treatment, and management, recognizing its potential in providing valuable insights into the disease.

The Effect of Bacillus coagulans Induced Interactions among Intestinal Bacteria, Metabolites, and Inflammatory Molecules in Improving Natural Skin Aging

BACKGROUND

Lactic acid bacteria consumption serves several health benefits to humans. However, their effect on natural skin aging is still unclear.

METHODS

This study examined the effects of skin naturalization (particularly skin drying) by administering a spore-bearing lactic acid bacteria (Bacillus coagulans) in mice for 2 years.

RESULTS

B. coagulans administration improved the natural skin of mice and significantly increased proportions of the genera Bacteroides and Muribaculum, among other intestinal bacteria. As metabolites, increases in nicotinic acid, putrescin, and pantothenic acid levels and a decrease in choline levels were observed. Increased hyaluronic acid, interleukin-10, and M2 macrophage levels indicate aging-related molecules in the skin. Intestinal permeability was also suppressed. Thus, these changes together improved natural skin aging.

CONCLUSIONS

This study revealed that B. coagulans administration improved the natural skin aging in mice. This enhancement might be induced by the interaction of alterations in intestinal flora, metabolites, or inflammatory substances.

The Role of Probiotics in Skin Health and Related Gut-Skin Axis: A Review

Aging skin, wrinkles, pigmentation, and dryness are problems that plague people, and researchers are working to solve them. Recent studies have shown that intestinal microbiota homeostasis can influence skin health, demonstrating the existence of a gut-skin axis. Recently, improving skin health through probiotic interventions has been proposed, and micro-ecological skin care is becoming a popular concept. By regulating skin health and gut-skin axis interactions, probiotics can be used as potential management tools to suppress and improve skin diseases in multiple ways, including decreasing oxidative stress, suppressing inflammatory responses, and keeping immune effects. The purpose of this paper is to provide a comprehensive review of the application and mechanisms of probiotic-mediated gut microbiota homeostasis in skin care and to offer a theoretical basis for the application of probiotics in skin care.

An Altered Skin and Gut Microbiota Are Involved in the Modulation of Itch in Atopic Dermatitis

Skin and gut microbiota play an important role in the pathogenesis of atopic dermatitis (AD). An alteration of the microbiota diversity modulates the development and course of AD, e.g., decreased microbiome diversity correlates with disease severity, particularly in lesional skin of AD. Itch is a hallmark of AD with unsatisfying treatment until now. Recent evidence suggests a possible role of microbiota in altering itch in AD through gut-skin-brain interactions. The microbial metabolites, proinflammatory cytokines, and impaired immune response lead to a modulation of histamine-independent itch, disruption of epidermal barrier, and central sensitization of itch mechanisms. The positive impact of probiotics in alleviating itch in AD supports this hypothesis, which may lead to novel strategies for managing itchy skin in AD patients. This review summarizes the emerging findings on the correlation between an altered microbiota and gut-skin-brain axis in AD, especially in modulating itchy skin.

Early intervention and prevention of allergic diseases

Food allergy (FA) is now one of the most common chronic diseases of childhood often lasting throughout life and leading to significant worldwide healthcare burden. The precise mechanisms responsible for the development of this inflammatory condition are largely unknown; however, a multifactorial aetiology involving both environmental and genetic contributions is well accepted. A precise understanding of the pathogenesis of FA is an essential first step to developing comprehensive prevention strategies that could mitigate this epidemic. As it is frequently preceded by atopic dermatitis and can be prevented by early antigen introduction, the development of FA is likely facilitated by the improper initial presentation of antigen to the developing immune system. Primary oral exposure of antigens allowing for presentation via a well-developed mucosal immune system, rather than through a disrupted skin epidermal barrier, is essential to prevent FA. In this review, we present the data supporting the necessity of (1) an intact epidermal barrier to prevent epicutaneous antigen presentation, (2) the presence of specific commensal bacteria to maintain an intact mucosal immune system and (3) maternal/infant diet diversity, including vitamins and minerals, and appropriately timed allergenic food introduction to prevent FA.

Skin damage caused by scale loss modifies the intestine of chronically stressed gilthead sea bream (Sparus aurata, L.)

The present study was designed to test if the damage caused by scale loss provokes a change in other innate immune barriers such as the intestine and how chronic stress affects this response. Sea bream (Sparus aurata) were kept in tanks at low density (16 kg m^-3, LD) or exposed to a chronic high density (45 kg m^-3, HD) stress for 4 weeks. Scales were then removed (approximately 50%) from the left flank in the LD and HD fish. Intestine samples (n = 8/group) were examined before and at 12 h, 3 days and 7 days after scale removal. Changes in the morphology of the intestine revealed that chronic stress and scale loss was associated with intestinal inflammation. Specifically, enterocyte height and the width of the lamina propria, submucosa and muscle layer were significantly increased (p < 0.05) 3 days after skin damage in fish under chronic stress (HD) compared to other treatments (LDWgut3d or HDgut0h). This was associated with a significant up-regulation (p < 0.05) in the intestine of gene transcripts for cell proliferation (pcna) and anti-inflammatory cytokine tgfβ1 and down-regulation of gene transcripts for the pro-inflammatory cytokines tnf-α and il1β (p < 0.05) in HD and LD fish 3 days after scale removal compared to the undamaged control (LDgut0h). Furthermore, a significant up-regulation of kit, a marker of mast cells, in the intestine of HDWgut3d and LDWgut3d fish suggests they may mediate the crosstalk between immune barriers. Skin damage induced an increase in cortisol levels in the anterior intestine in HDWgut12 h fish and significant (p < 0.05) down-regulation of mr expression, irrespective of stress. These results suggest glucocorticoid levels and signalling in the intestine of fish are modified by superficial cutaneous wounds and it likely modulates intestine inflammation.

Comparative Analysis of the Microbiome across the Gut-Skin Axis in Atopic Dermatitis

Atopic dermatitis (AD) is a refractory and relapsing skin disease with a complex and multifactorial etiology. Various congenital malformations and environmental factors are thought to be involved in the onset of the disease. The etiology of the disease has been investigated, with respect to clinical skin symptoms and systemic immune response factors. A gut microbiome–mediated connection between emotional disorders such as depression and anxiety, and dermatologic conditions such as acne, based on the comorbidities of these two seemingly unrelated disorders, has long been hypothesized. Many aspects of this gut–brain–skin integration theory have recently been revalidated to identify treatment options for AD with the recent advances in metagenomic analysis involving powerful sequencing techniques and bioinformatics that overcome the need for isolation and cultivation of individual microbial strains from the skin or gut. Comparative analysis of microbial clusters across the gut–skin axis can provide new information regarding AD research. Herein, we provide a historical perspective on the modern investigation and clinical implications of gut–skin connections in AD in terms of the integration between the two microbial clusters.

Gut-Skin Axis: Current Knowledge of the Interrelationship between Microbial Dysbiosis and Skin Conditions

The microbiome plays an important role in a wide variety of skin disorders. Not only is the skin microbiome altered, but also surprisingly many skin diseases are accompanied by an altered gut microbiome. The microbiome is a key regulator for the immune system, as it aims to maintain homeostasis by communicating with tissues and organs in a bidirectional manner. Hence, dysbiosis in the skin and/or gut microbiome is associated with an altered immune response, promoting the development of skin diseases, such as atopic dermatitis, psoriasis, acne vulgaris, dandruff, and even skin cancer. Here, we focus on the associations between the microbiome, diet, metabolites, and immune responses in skin pathologies. This review describes an exhaustive list of common skin conditions with associated dysbiosis in the skin microbiome as well as the current body of evidence on gut microbiome dysbiosis, dietary links, and their interplay with skin conditions. An enhanced understanding of the local skin and gut microbiome including the underlying mechanisms is necessary to shed light on the microbial involvement in human skin diseases and to develop new therapeutic approaches.

A decrease in the tear secretion volume in a mouse model with ulcerative colitis

PURPOSE

Dry eye syndrome is known to develop from several systemic inflammatory diseases. Although dry eye may develop due to extraintestinal complications of ulcerative colitis (UC), the pathogenesis is not well-known. This study aimed to investigate whether there was decrease in the tear secretion volume in a mice model with UC; the difference between the control and dextran sodium sulphate (DSS)-treated group was also determined.

MATERIALS AND METHODS

This study included a mice model with UC induced by the oral administration of 5.0% DSS for 7 days. Following the DSS treatment, the tear volume was measured using the Schirmer's test. The colon and ocular tissues, including the lacrimal gland, were evaluated using histological and protein analyses. Additionally, tumour necrosis factor (TNF)-α and interleukin (IL)-6 in the plasma were determined. Differences between groups (DSS-treated versus control mice) were determined using Student's t-test.

RESULTS

The tear volume in DSS-treated mice was decreased compared to that in the control mice. Plasma levels of TNF-α and IL-6 in DSS-treated mice was higher than that of control. Morphological change was observed with the invasion of the inflammatory cell in the lacrimal gland of DSS-treated mice. Terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labelling (TUNEL)-positive cells were increased in the lacrimal glands of DSS-treated mice compared with control group. The distribution of aquaporin-5 expressed in the lacrimal gland of DSS-treated mice was decreased compared to that in the control group.

CONCLUSIONS

These findings suggest that a decrease in the tear volume in UC was associated with a functional decline in the inflamed lacrimal gland. This result therefore provides useful information that could contribute to the development of treatment approaches for dry eye associated with UC.

Role of Momordica charantia in preventing the natural aging process of skin and sexual organs in mice

Although various methods for improving the natural aging of skin have been examined, an effective method is currently unavailable. Therefore, in this study, we investigated the effects of Momordica charantia on the natural aging of skin of mice and how sex differences influenced these effects. To this end, we bred female and male hairless mice without ultraviolet ray irradiation and physical stress for 2 years. During the study period, mice were orally administered 50 mg/kg/day Momordica charantia fruit extract, three times per week. The characteristics of naturally aging skin, in terms of moisture retention, hydration, thickness, and reduced wrinkle score, improved after Momordica charantia treatment in both male and female mice. Furthermore, reduced cell apoptosis was observed in the female ovaries and male testes, and the levels of testosterone and 17β-estradiol in blood were maintained. After treatment with Momordica charantia, the expression of matrix metalloprotease (MMP)-1 and hyaluronidase (HAYL)2 decreased in the skin of female mice, whereas the serum levels of interleukin (IL)-33 increased in the male mice. These results indicated that the natural aging of the skin was decelerated by Momordica charantia via regulation of the 17β-estradiol/mast cell/MMP-1/HAYL2 and testosterone/mast cell/IL-33 signaling pathways in female and male mice, respectively.

Adverse Reaction of Dextran Sodium Sulfate-Induced Colitis in a Collagen-Induced Mouse Arthritis Model

The pathogenic relationship of ulcerative colitis and rheumatoid arthritis is not known. Therefore, we examined dextran sodium sulfate (DSS)-induced colitis separately and in combination with a mouse arthritis model that mimics rheumatoid arthritis and evaluated the deterioration-related factors of each condition. Arthritis was induced in a collagen-induced arthritis mouse model using DBA/1JJmsSlc mice and ulcerative colitis was induced by the administration of drinking water containing 3.0% (w/v) DSS. The arthritis/DSS-treated mice developed worse colitis scores compared to that of the other groups of mice. The arthritis/DSS-treated mice did not demonstrate changes in hind foot volumes or in the concentration of matrix metalloproteinase-3 (MMP-3) in the plasma; however, plasma levels of interleukin-6 (IL-6) and tumor necrosis factor (TNF)-α were increased. Our results showed that IL-6 and TNF-α may influence the deterioration effect of colitis in arthritic mice.

Impaired skin barrier function caused by reactive oxygen species in mice with colonic tumours

Purpose: We have previously reported that skin barrier function is disrupted in mice with colonic tumours induced by azoxymethane (AOM) and dextran sodium sulphate (DSS). We postulated that the impaired skin barrier function was associated with reactive oxygen species derived from gp91phox. In this study, we investigated the mechanisms underlying the impaired skin barrier function using gp91phox-/- mice. Materials and methods: We induced colonic tumorigenesis in C57BL/6j mice by AOM + DSS administration and evaluated the influence of reactive oxygen species on skin barrier function by using the hydroxyl radical scavenger N-acetyl-l-cysteine (NAC) or gp91phox-/- mice. Damage to the colon and skin following treatment with AOM + DSS was monitored using protein analysis methods and by detection of inflammatory mediators in the plasma. Results: NAC could not prevent the increase in transepidermal water loss (TEWL) and decrease in skin hydration level caused by AOM + DSS in gp91phox+/+ mice. However, gp91phox-/- mice showed no change in TEWL and skin hydration level. The dermal expression levels of nucleotide-binding domain, leucine-rich containing family, pyrin-domain containing 3 (NLRP3), and caspase-1 were reduced in gp91phox-/- mice. Moreover, the plasma concentrations of interleukin-18 and thymic stromal lymphopoietin (TSLP) were lower in gp91phox-/- mice than those in gp91phox+/+ mice. Inhibition of hydrogen peroxide production from superoxide anions in the gp91phox-/- status prevented the increased TEWL and decreased skin hydration level noted with degradation of NLRP3 and caspase-1. Conclusions: Superoxide anions may play an important role in the onset of the impaired skin barrier function in mice with colonic tumours.

Microbiome in the Gut-Skin Axis in Atopic Dermatitis

The microbiome is vital for immune system development and homeostasis. Changes in microbial composition and function, termed dysbiosis, in the skin and the gut have recently been linked to alterations in immune responses and to the development of skin diseases, such as atopic dermatitis (AD). In this review, we summarize the recent findings on the gut and skin microbiome, highlighting the roles of major commensals in modulating skin and systemic immunity in AD. Although our understanding of the gut-skin axis is only beginning, emerging evidence indicates that the gut and skin microbiome could be manipulated to treat AD.

Influence of Repeated Senna Laxative Use on Skin Barrier Function in Mice

Background

Senna, one of the major stimulant laxatives, is widely used for treating constipation. Chronic senna use has been reported to be associated with colonic disorders such as melanosis coli and/or epithelial hyperplasia. However, there is no obvious information on the influence of chronic senna use on organs except for the intestine.

Objective

To clarify the influence of senna laxative use on skin barrier function by repeated senna administration.

Methods

Eight-week-old male hairless mice received senna (10 mg/kg/day) for 21 days. After administration, we evaluated transepidermal water loss (TEWL), and investigated the biomarkers in plasma and skin using protein analysis methods.

Results

Fecal water content on day seven was significantly increased; however, on day 21, it was significantly decreased after repeated senna administration. In the senna-administered group, TEWL was significantly higher compared to the control on days seven and 21. Plasma acetylcholine concentration and NO₂⁻/NO₃⁻ were increased on days seven and 21, respectively. In skin, tryptase-positive mast cells and inducible nitric oxide synthase (iNOS)-positive cells were increased on days seven and 21, respectively. The increase of TEWL on days seven and 21 was suppressed by the administration of atropine and N(G)-nitro-L-arginine methyl ester, respectively.

Conclusion

It was suggested that diarrhea or constipation induced by repeated senna administration caused the impairment of skin barrier function. There is a possibility that this impaired skin barrier function occurred due to degranulation of mast cells via cholinergic signals or oxidative stress derived from iNOS.

Role of mast cells in the induction of dry skin in a mouse model of rheumatoid arthritis

PURPOSE

Rheumatoid arthritis (RA) is known to induce dry skin as an extra-articular symptom. However, the mechanisms behind the induction are unclear. In this study, we utilized an arthritis mouse model to simulate RA to reveal the relationship between arthritis and dry skin.

MATERIALS AND METHODS

DBA/1JJmsSlc control mice (n = 5) and DBA/1JJmsSlc collagen-induced arthritis mouse model (arthritis mice; n = 5) were used. We measured transepidermal water loss (TEWL) and capacitance to reveal the effect of arthritis on skin barrier function. In addition, we measured the expression of biomarkers of skin barrier function.

RESULTS

We found that the hind limb volume of the arthritis mice was higher than that of the control mice. Our results showed that the arthritis mice had higher TEWL and lower capacitance when compared to the control mice. When compared to that of the control mice, the skin of the arthritis mice was thicker with more leukocyte infiltration. In the skin of arthritis mice, we observed lower expression of type I and IV collagens, but higher expression of matrix metalloproteinases (MMP)-1 and -9 when compared to that of the control mice. The levels of mast cells, histamine, substance P, and tryptase were higher in the arthritis mice than in the control mice. This study showed that the arthritis mice exhibited a disruption of skin barrier function (i.e. dry skin), which was improved following treatment with a mast cell inhibitor.

CONCLUSIONS

Our results on mast cells suggested that an improvement of dry skin is important for RA management.

The gut-skin axis in health and disease: A paradigm with therapeutic implications

As crucial interface organs gut and skin have much in common. Therefore it is unsurprising that several gut pathologies have skin co-morbidities. Nevertheless, the reason for this remains ill explored, and neither mainstream gastroenterology nor dermatology research have systematically investigated the 'gut-skin axis'. Here, in reviewing the field, we propose several mechanistic levels on which gut and skin may interact under physiological and pathological circumstances. We focus on the gut microbiota, with its huge metabolic capacity, and the role of dietary components as potential principle actors along the gut-skin axis. We suggest that metabolites from either the diet or the microbiota are skin accessible. After defining open key questions around the nature of these metabolites, how they are sensed, and which cutaneous changes they can induce, we propose that understanding of these pathways will lead to novel therapeutic strategies based on targeting one organ to improve the health of the other.