The Skin Microbiome: Is It Affected by UV-induced Immune Suppression?

Exploring the impact of solar radiation on skin microbiome to develop improved photoprotection strategies

The skin microbiome undergoes constant exposure to solar radiation (SR), with its effects on health well-documented. However, understanding SR's influence on host-associated skin commensals remains nascent. This review surveys existing knowledge on SR's impact on the skin microbiome and proposes innovative sun protection methods that safeguard both skin integrity and microbiome balance. A team of skin photodamage specialists conducted a comprehensive review of 122 articles sourced from PubMed and Research Gateway. Key terms included skin microbiome, photoprotection, photodamage, skin cancer, ultraviolet radiation, solar radiation, skin commensals, skin protection, and pre/probiotics. Experts offered insights into novel sun protection products designed not only to shield the skin but also to mitigate SR's effects on the skin microbiome. Existing literature on SR's influence on the skin microbiome is limited. SR exposure can alter microbiome composition, potentially leading to dysbiosis, compromised skin barrier function, and immune system activation. Current sun protection methods generally overlook microbiome considerations. Tailored sun protection products that prioritize both skin and microbiome health may offer enhanced defense against SR-induced skin conditions. By safeguarding both skin and microbiota, these specialized products could mitigate dysbiosis risks associated with SR exposure, bolstering skin defense mechanisms and reducing the likelihood of SR-mediated skin issues.

Microbiome modulators for atopic eczema: a systematic review of experimental and investigational therapeutics

INTRODUCTION

Atopic dermatitis (AD) is a common inflammatory cutaneous disease that arises due to dysregulation of the Th2 immune response, impaired skin barrier integrity, and dysbiosis of the skin and gut microbiota. An abundance of Staphylococcus aureus biofilms in AD lesions increases the Th2 immune response, and gut bacteria release breakdown products such as Short Chain Fatty Acids that regulate the systemic immune response.

AREAS COVERED

We aim to evaluate therapies that modulate the microbiome in humans and discuss the clinical implications of these treatments. We performed a review of the literature in which 2,673 records were screened, and describe the findings of 108 studies that were included after full-text review. All included studies discussed the effects of therapies on the human microbiome and AD severity. Oral probiotics, topical probiotics, biologics, and investigational therapies were included in our analysis.

EXPERT OPINION

Oral probiotics demonstrate mixed efficacy at relieving AD symptoms. Topical probiotics reduce S. aureus abundance in AD lesional skin, yet for moderate-severe disease, these therapies may not reduce AD severity scores to the standard of biologics. Dupilumab and tralokinumab target key inflammatory pathways in AD and modulate the skin microbiome, further improving disease severity.

Eradication of skin microbiota restores cytokine production and release in polymorphic light eruption

Polymorphic light eruption (PLE) has been mechanistically linked to cytokine abnormalities. Emerging preclinical evidence posits the skin microbiome as a critical modulator of ultraviolet (UV)-induced cytokine expression, thereby influencing subsequent immune responses. This intricate relationship remains underexplored in the context of PLE. Hence, we investigated the differential responses between disinfected and non-disinfected skin following both single and repetitive exposures to solar-simulated UV radiation in patients with PLE. An experimental, half-body pilot study was conducted involving six PLE patients and 15 healthy controls. Participants' skin was exposed to single and multiple doses of solar-simulated UV radiation, both in disinfected and in non-disinfected skin areas. The co-primary outcomes were PLE score and cytokine expression in blister fluid analysed through OLINK proteomic profiling. Secondary outcomes were erythema, pigmentation, induction of apoptotic cells in vacuum-generated suction blisters, and density of infiltrate in skin biopsies of PLE patients. Among the 71 cytokines analysed, baseline expression levels of 20 specific cytokines-integral to processes such as apoptosis, inflammation, immune cell recruitment, cellular growth, and differentiation-were significantly impaired in PLE patients compared with healthy controls. Notably, skin disinfection reversed the observed cytokine imbalances following a single UV exposure at the minimal erythema dose (MED) level and exhibited even more pronounced effects after multiple UV exposures. However, no significant differences were evident in PLE score, erythema, pigmentation, or rates of apoptotic cell induction upon UV radiation. These findings provide evidence for UV-driven cytokine regulation by the skin microbiota and imply microbiome involvement in the PLE immune response.

Sunscreens can preserve human skin microbiome upon erythemal UV exposure

OBJECTIVE

Ultraviolet radiation (UVR) is a known environmental key factor for premature skin ageing. Only few scientific evidence is available to support the effects of UVR on the skin microbiome. This in vivo pilot study aimed to evaluate the impact on the skin microbiome upon erythemal UV exposure and the protection of UV-exposed skin microbiome by UV filters.

METHODS

Ten female volunteers were treated with an sun protection factor (SPF) 20 sunscreen and placebo formulation (without UV filters) on their upper middle backs and irradiated with an erythemal dose (2 MED) by a solar simulator. Skin swabbing samples from four zones (i.e., unexposed, exposed, sunscreen- and placebo-treated on exposed skin) were collected for the microbiome analysis before and 2 h after UV exposure, respectively, and processed via shallow 16S rRNA Amplicon and Shotgun metagenomic sequencing. An in vitro UV method was developed to confirm the protection of isolated bacterial strains by single UV filters and combinations.

RESULTS

Alpha diversity was impacted by significant inter-individual differences and by treatment rather than by irradiation. Cutibacterium acnes was found to be the most abundant and a confounding factor for diversity. On a species level, Lactobacillus crispatus was negatively associated with UVR and placebo treatment, whereas there was a positive association with sunscreen treatment. The sunscreen treatment also favoured an interaction network with central Micrococcus genus. The in vitro results showed that both single UV filters and combinations had specific effects on the survival rates of L. crispatus, C. acnes, and Staphylococcus epidermidis.

CONCLUSION

We identified potential microorganisms and bacterial interactions that were associated with an SPF 20 sunscreen treatment. The specific protection of L. crispatus as a key player in the UV-exposed skin microbiome and reduction of C. acnes population by UV filters might lead to new cosmetic concepts for photoprotection.

A narrative review of the impact of ultraviolet radiation and sunscreen on the skin microbiome

BACKGROUND

The human skin microbiome is a dynamic ecosystem that plays an important role in skin health. The skin microbiome has been implicated in numerous diseases, and our knowledge surrounding it continues to evolve. A better understanding of the interactions between the environment and the skin microbiome will lead to improvements in skin health.

METHODS

This article reviews the published literature surrounding the impact of ultraviolet radiation (UVR) and sunscreen on the skin microbiome.

RESULTS

Skin microbes are differentially impacted by UVR, and alterations in the microbiome can be detected following UVR exposure. These changes are related to direct bactericidal effects, alterations in the cutaneous metabolome, and changes in the cutaneous immune system. UV filters used in sunscreen have been shown to have bactericidal effects, and many compounds used in sunscreen emulsions can also negatively impact cutaneous microbes.

CONCLUSION

A healthy microbiome has been shown to produce compounds that help protect the skin from UVR, and sunscreen has the potential to reduce the diversity of the skin microbiome. This indicates that designing sunscreen products that both provide protection against UVR and preserve the skin microbiome may offer additional benefits to skin health when compared with traditional sunscreen products.

Behaviour and sun exposure in holidaymakers alters skin microbiota composition and diversity

Introduction: The skin microbiota plays a crucial role in maintaining epidermal homeostasis. Ultraviolet radiation (UVR) and other environmental challenges can impact the skin microbiota through direct and indirect mechanisms. This study aimed to investigate the effects of sun exposure on the skin microbiota and its relationship with individual skin phototypes. Methods: Healthy volunteers (n = 21 [4M, 17 F], mean age 33.2 years) holidayed in a sunny destination for a minimum of 7 days with swabs taken pre-holiday and up to 84 days post-holiday. Participant group was categorised by individual typology angle (ITA) classification and the composition of the skin microbiota was examined using 16S rRNA gene sequencing. Results: In the entire cohort and at all time points, the major bacterial phyla were Actinobacteria, Proteobacteria and Firmicutes. There was a significant change in microbial beta diversity at day 28 post-holiday, compared to baseline, for all participants. However, when participants were segregated into three cohorts dependent on the degree of skin tanning response between baseline (pre-holiday) and immediately one-day post-holiday, there was a reduction in Proteobacteria in the sun-seeking participants 1 day after the holiday, which recovered over time. Discussion: These findings suggest that sun exposure can affect the diversity and composition of the skin microbiota, which may have downstream effects on skin health.

Probiotics in Orthopedics: From Preclinical Studies to Current Applications and Future Perspective

In recent years, probiotics have been emerging as an attractive therapeutic strategy for several diseases. In orthopedics, probiotics seem to be a promising supplementation for treatment of osteoporosis, osteoarthritis, muscle loss-related disease, wound and ulcer issues, and prevention of surgical antibiotic prophylaxis side effects. Although probiotics are still not included in guidelines for these conditions, several studies have reported theoretical benefits of their administration. Further high-level clinical trials are necessary to convert research into solid clinical practice. However, probiotics represent a cost-effective future perspective and may play a role in association with traditional orthopedic therapies.

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.

Climate Change, Skin Health, and Dermatologic Disease: A Guide for the Dermatologist

Climate change has a pervasive impact on health and is of clinical relevance to every organ system. Climate change-related factors impact the skin's capacity to maintain homeostasis, leading to a variety of cutaneous diseases. Stratospheric ozone depletion has led to increased risk of melanoma and keratinocyte carcinomas due to ultraviolet radiation exposure. Atopic dermatitis, psoriasis, pemphigus, acne vulgaris, melasma, and photoaging are all associated with rising levels of air pollution. Elevated temperatures due to global warming induce disruption of the skin microbiome, thereby impacting atopic dermatitis, acne vulgaris, and psoriasis, and high temperatures are associated with exacerbation of skin disease and increased risk of heat stroke. Extreme weather events due to climate change, including floods and wildfires, are of relevance to the dermatologist as these events are implicated in cutaneous injuries, skin infections, and acute worsening of inflammatory skin disorders. The health consequences as well as the economic and social burden of climate change fall most heavily on vulnerable and marginalized populations due to structural disparities. As dermatologists, understanding the interaction of climate change and skin health is essential to appropriately manage dermatologic disease and advocate for our patients.

Role of Cutaneous Microbiome in Dermatology

The cutaneous microflora consists of various microorganisms which interact with host epithelial cells and innate and acquired immunity. This microbial milieu and its interaction with host cells prevent the growth of pathogenic organisms and educate host immunity to fight against harmful microorganisms. The microbial composition depends on various intrinsic and extrinsic factors and an imbalance in the cutaneous microflora predisposes the individual to both infectious and non-infectious diseases. Even though probiotics have been extensively studied in various diseases, their efficacy and safety profile are still unclear. A better understanding of the cutaneous microflora is required to develop newer therapeutic targets. In this review, we describe the commensal microbiome and its variation, the current role of the cutaneous microbiome in the pathogenesis of various dermatological diseases, and their therapeutic implications.

Flavonoids as Promising Natural Compounds in the Prevention and Treatment of Selected Skin Diseases

Phytochemicals represent a large and diverse group of naturally occurring compounds, bioactive nutrients, or phytonutrients produced by plants, widely found in fruits, vegetables, whole grains products, legumes, beans, herbs, seeds, nuts, tea, and dark chocolate. They are classified according to their chemical structures and functional properties. Flavonoids belong to the phenolic class of phytochemicals with potential solid pharmacological effects as modulators of multiple signal transduction pathways. Their beneficial effect on the human body is associated with their antioxidant, anti-inflammatory, antimutagenic, and anticarcinogenic properties. Flavonoids are also widely used in various nutritional, pharmaceutical, medical, and cosmetic applications. In our review, we discuss the positive effect of flavonoids on chronic skin diseases such as vitiligo, psoriasis, acne, and atopic dermatitis.

The Imprint of Exposome on the Development of Atopic Dermatitis across the Lifespan: A Narrative Review

Atopic dermatitis (AD) is a chronic inflammatory skin condition that affects more than 200 million people worldwide, including up to 20% of children and 10% of the adult population. Although AD appears frequently in childhood and often continues into adulthood, about 1 in 4 adults develop the adult-onset disease. The prenatal period, early childhood, and adolescence are considered critical timepoints for the development of AD when the exposome results in long-lasting effects on the immune system. The exposome can be defined as the measure of all the exposures of an individual during their lifetime and how these exposures relate to well-being. While genetic factors could partially explain AD onset, multiple external environmental exposures (external exposome) in early life are implicated and are equally important for understanding AD manifestation. In this review, we describe the conceptual framework of the exposome and its relevance to AD from conception and across the lifespan. Through a spatiotemporal lens that focuses on the multi-level phenotyping of the environment, we highlight a framework that embraces the dynamic complex nature of exposome and recognizes the influence of additive and interactive environmental exposures. Moreover, we highlight the need to understand the developmental origins of AD from an age-related perspective when studying the effects of the exposome on AD, shifting the research paradigm away from the per se categorized exposome factors and beyond clinical contexts to explore the trajectory of age-related exposome risks and hence future preventive interventions.

Climate change, the cutaneous microbiome and skin disease: implications for a warming world

The skin plays an important role in human health by providing barrier protection against environmental stressors. In addition to human skin cells, the cutaneous barrier is also home to a network of organisms that have co-evolved with humans, referred to as the cutaneous microbiome. This network has been demonstrated to play an active role in skin health and the manifestation of cutaneous disease. Here, we review how a warming world and its attendant changes in climatic variables, including temperature, humidity, ultraviolet radiation, and air pollution, influence the cutaneous microbiome and, in turn, skin health. Studies indicate that the cutaneous microbiome is affected by these factors, and these changes may influence the epidemiology and severity of cutaneous disorders including atopic dermatitis, acne vulgaris, psoriasis, and skin cancer. Further investigation into how the cutaneous microbiome changes in response to climate change and subsequently influences skin disease is needed to better anticipate future dermatologic needs and potentially generate novel therapeutic solutions in response.

PD-L1 Enhanced by cis-Urocanic Acid on Langerhans Cells Inhibits Vγ4+ γδT17 Cells in Psoriatic Skin Inflammation

Psoriasis is an IL-23/IL-17-mediated inflammatory autoimmune dermatosis and ultraviolet B (UVB) may contribute to immunosuppression and ameliorate associated symptoms. One of the pathophysiology underlying UVB therapy is through the production of cis-urocanic acid (cis-UCA) from keratinocytes. However, the detailed mechanism is yet to be fully understood. In the current study, we found filaggrin expression and serum cis-UCA levels were significantly lower in psoriasis patients than in healthy controls. We also noted that cis-UCA application inhibited psoriasiform inflammation through the reduction of Vγ4⁺ γδT17 cells in murine skin and draining lymph nodes. Meanwhile, CCR6 was down-regulated on γδT17 cells, which would suppress the inflammatory reaction at a distal skin site. We revealed that 5-HT_2A receptor (HTR2A), the known cis-UCA receptor, was highly expressed on Langerhans cells (LCs) in the skin. cis-UCA also inhibited IL-23 expression and induced PD-L1 on LCs, leading to the attenuated proliferation and migration of γδT cells. Compared to the isotype control, α-PD-L1 treatment in vivo could reverse the anti-psoriatic effects of cis-UCA. PD-L1 expression on LCs was sustained through cis-UCA-induced MAPK/ERK pathway. These findings uncover the cis-UCA-induced PD-L1-mediated immunosuppression on LCs, which facilitates the resolution of inflammatory dermatoses.

Probiotic growth in skin-like conditions

Although probiotics' main known effects are in the digestive system, over the last years several benefits that come from their topical use, have been investigated. Several studies have reported beneficial effects on different skin disorders, such as atopic dermatitis, acne, eczema, psoriasis, wound healing, skin aging and reactive skin. Their main action is assigned to the inhibition of skin colonization by pathogens. In this work, the growths of three probiotic strains were evaluated in the presence of abiotic factors similar to those found in skin, namely, UV radiation, temperature, pH, NaCl and fatty acids. Lactobacillus rhamnosus showed increased growth under the pH of 6, but no differences in its growth were found for the various NaCl concentrations tested. Lactobacillus delbrueckii increased the number of bacterial cells in 88.8% when grown in 10 mM NaCl concentration, while Propioniferax innocua showed increased growth at 45 °C. All tested probiotic bacteria were able to grow under skin-like conditions. However, L. rhamnosus was the probiotic that showed the best results. The results obtained in this study indicate that the used probiotics may be beneficial in the treatment of skin diseases, since they are able to successfully thrive in skin-like conditions.

Effect of Solar Radiation on Skin Microbiome: Study of Two Populations

Here, we examined the skin microbiome of two groups of healthy volunteers living on the Mediterranean coast with different exposures to sun radiation. One group, exposed to the sun in the summer, was compared with a group covered with clothing throughout the year. The seasonal effects on the skin microbiome of three body sites were determined before and after summer. Surprisingly, at the phyla level, there were no significant differences in microbiome diversity between the groups. Furthermore, within each group, there were no significant seasonal differences in high-abundance species at any of the sampling sites. These results suggest that the skin microbiome, developed over years, remains stable even after several months of exposure to summer weather, direct sunlight and humidity. However, in the group exposed to the sun during the summer months, there were significant differences in low-abundance species in sun-exposed areas of the skin (the inner and outer arm). These subtle changes in low-abundance species are interesting, and their effect on skin physiology should be studied further.

5-α reductase inhibition by Epilobioum fleischeri extract modulates facial microbiota structure

Background

Facial skin is a particularly complex environment made of different skin types such as sebaceous (forehead) and dry (cheeks). The skin microbiota composition on different facial sites has not yet been addressed.

Methods

We conducted a 4‐week‐long, single‐centre, randomized and placebo‐controlled clinical study involving 23 Caucasian females. We assessed both bacterial composition on five different facial areas and the microbiome modulatory effects resulting from the topical application of a plant extract (Epilobium fleischeri). Skin microbiome samples were collected before and after 4 weeks of product application. Microbiota profiling was performed via 16S rRNA gene sequencing, and relative abundance data were used to calculate differentials via a multinomial regression model.

Results

Via ‘reference frames’, we observed shifts in microbial composition after 4 weeks of twice‐daily product application and identify certain microbiota species, which were positively associated with the application of the product containing the Epilobium fleischeri extract. Staphylococcus hominis, Staphylococcus epidermidis, and Micrococcus yunnanensis appeared to be significantly enriched in the final microbiota composition of the active treatment group.

Conclusion

Facial skin was found to be colonized by an heterogenous microbiota, and the Epilobium fleischeri extract had a modulatory effect on commensal bacteria on the different facial sites.

Bacterial taxa predictive of hyperpigmented skins

Background and Aims

Dark spots, brown spots, or hyperpigmented spots (HPS) are oval or irregular brown areas of skin. Their emergence is associated with dysregulation of the immune system, and may also be caused by a deficiency in stromal cell‐derived factor‐1, leading to perturbed melanogenesis and accumulation of melanosomes within neighboring keratinocytes. The skin microbiota (living microorganisms present on the surface of the skin) is known to play essential roles in maintaining skin homeostasis and in regulating the immune system. Here, we investigated whether the microbiota could play a role in the emergence of HPS.

Methods

The clinical study involved 38 European women, selected from among 74 volunteers. Participants were divided into two groups depending on the spot areas measured on their faces. The study was designed to avoid conflicting factors: both groups presented similar skin pH, hydration, transepidermal water loss, and sebum levels. The two cohorts were also age‐matched, with a mean of 29‐years‐old for both.

Results

Alpha‐diversity of the microbiota was similar for the two groups. On skins with more HPS, seven bacterial genera were identified in significantly higher proportions and included opportunistic pathogens and inflammatory bacteria. Six bacterial genera, including bacteria showing antioxidant and anti‐UV properties, were identified in significantly higher proportions on less spotted skins. Cross‐domain association networks revealed distinct co‐occurrences of genera between the two groups, suggesting nonidentical community structures and exchanges, depending on the HPS status.

Conclusion

Our results reveal specific microbiota composition and networks on skins based on HPS status. Changes could alter communication with the immune system, leading to the emergence of dark spots. As an essential part of the overall skin ecosystem, and through its interaction with the skin matrix, the skin microbiota and its maintenance could be considered a new target for skincare applications.

Cold atmospheric pressure plasma for attenuation of SARS-CoV-2 spike protein binding to ACE2 protein and the RNA deactivation

Cold atmospheric pressure (CAP) plasma has a profound effect on protein–protein interactions. In this work, we have highlighted the deactivation of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) spike protein by CAP plasma treatment. Complete deactivation of spike protein binding to the human ACE2 protein was observed within an exposure time of 5 minutes which is correlated to the higher concentration of hydrogen peroxide formation due to the interaction with the reactive oxygen species present in the plasma. On the other hand, we have established that CAP plasma is also capable of degrading RNA of SARS-CoV-2 virus which is also linked to hydrogen peroxide concentration. The reactive oxygen species is produced in the plasma by using noble gases such as helium, in the absence of any other chemicals. Therefore, it is a green process with no chemical waste generated and highly advantageous from the environmental safety prospects. Results of this work could be useful in designing plasma-based disinfection systems over those based on environmentally hazardous chemical-based disinfection and biomedical applications.

Cold atmospheric pressure (CAP) plasma for the deactivation of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) spike protein binding to ACE2 protein.

Illuminating Human Norovirus: A Perspective on Disinfection of Water and Surfaces Using UVC, Norovirus Model Organisms, and Radiation Safety Considerations

Human noroviruses (HuNoVs) are a major cause of gastroenteritis and are associated with high morbidity because of their ability to survive in the environment and small inoculum size required for infection. Norovirus is transmitted through water, food, high touch-surfaces, and human-to-human contact. Ultraviolet Subtype C (UVC) light-emitting diodes (LEDs) can disrupt the norovirus transmission chain for water, food, and surfaces. Here, we illuminate considerations to be adhered to when picking norovirus surrogates for disinfection studies and shine light on effective use of UVC for norovirus infection control in water and air and validation for such systems and explore the blind spot of radiation safety considerations when using UVC disinfection strategies. This perspective also discusses the promise of UVC for norovirus mitigation to save and ease life.

Advances in Microbiome-Derived Solutions and Methodologies Are Founding a New Era in Skin Health and Care

The microbiome, as a community of microorganisms and their structural elements, genomes, metabolites/signal molecules, has been shown to play an important role in human health, with significant beneficial applications for gut health. Skin microbiome has emerged as a new field with high potential to develop disruptive solutions to manage skin health and disease. Despite an incomplete toolbox for skin microbiome analyses, much progress has been made towards functional dissection of microbiomes and host-microbiome interactions. A standardized and robust investigation of the skin microbiome is necessary to provide accurate microbial information and set the base for a successful translation of innovations in the dermo-cosmetic field. This review provides an overview of how the landscape of skin microbiome research has evolved from method development (multi-omics/data-based analytical approaches) to the discovery and development of novel microbiome-derived ingredients. Moreover, it provides a summary of the latest findings on interactions between the microbiomes (gut and skin) and skin health/disease. Solutions derived from these two paths are used to develop novel microbiome-based ingredients or solutions acting on skin homeostasis are proposed. The most promising skin and gut-derived microbiome interventional strategies are presented, along with regulatory, safety, industrial, and technical challenges related to a successful translation of these microbiome-based concepts/technologies in the dermo-cosmetic industry.

[Herpes simplex factors: Literature review]

Herpes simplex virus, after the first infection, can remain dormant in the lymph nodes and reactivate at any time due to certain factors and/or stimuli causing effects in the patient. The purpose of this literature review is to update scientific information on the factors that predispose to the reactivation of herpes simplex virus. A comprehensive literature review was conducted in the LILACS, SciELO, PubMed, Scopus and the following keywords were used: herpes simplex, reactivation, latency and risks. A factor is reactivation by immunosuppression due to the intake of immunosuppressants or oncological therapy. Another factor is psychological stress, in which the hormones released act on mediating signs of reactivation. Sun exposure that reactivates the virus in infected neurons and infection in pregnant women can trigger complications in the fetus and delivery.

Immunopathogenesis and management of polymorphic light eruption

Polymorphic light eruption (PLE) is the most common immunologically mediated photodermatosis, demonstrating many abnormalities caused by critical failure of ultraviolet (UV)-induced immunosuppression. The unique expression of antimicrobial peptides in PLE, which is most likely determined by alteration of microbiome components upon UV exposure, implicates their possible triggering role and pathogenic significance in the eruption. The review aims to clarify current knowledge regarding the immunological disturbances correlated with PLE that serve a base for better understanding of molecular pathogenesis of the disease and the development of new therapeutic strategies. Preventive treatment with broad-spectrum suncreens and sunscreens containing DNA repair enzymes, as well as natural photohardening with graduate exposure to sunlight in early spring could be sufficient in milder cases. Antioxidants and topical calcipotriol are promising approach for adjuvant prevention. Phototherapy, mainly with narrow band UVB rays, is more appropriate method in severe cases of the disease. The established treatment options for PLE include local and systemic glucocorticoids, systemic nonsedative antihistamines for itch relief, and rarely, immunosuppressive drugs in the refractory cases. Like medical photohardening, afamelanotide has the potential of photoprotection by inducing a melanization of the skin. Afamelanotide is believed to be a possible new treatment option for very severe and refractory cases of PLE. Targeting the main pruritogenic cytokine, IL-31, opens a new road for the development of novel therapeutic approaches to combat moderate and severe itching in cases of PLE with intense pruritus.

Microbiome Modulation as a Therapeutic Approach in Chronic Skin Diseases

There is a growing quantity of evidence on how skin and gut microbiome composition impacts the course of various dermatological diseases. The strategies involving the modulation of bacterial composition are increasingly in the focus of research attention. The aim of the present review was to analyze the literature available in PubMed (MEDLINE) and EMBASE databases on the topic of microbiome modulation in skin diseases. The effects and possible mechanisms of action of probiotics, prebiotics and synbiotics in dermatological conditions including atopic dermatitis (AD), psoriasis, chronic ulcers, seborrheic dermatitis, burns and acne were analyzed. Due to the very limited number of studies available regarding the topic of microbiome modulation in all skin diseases except for AD, the authors decided to also include case reports and original studies concerning oral administration and topical application of the pro-, pre- and synbiotics in the final analysis. The evaluated studies mostly reported significant health benefits to the patients or show promising results in animal or ex vivo studies. However, due to a limited amount of research and unambiguous results, the topic of microbiome modulation as a therapeutic approach in skin diseases still warrants further investigation.

Oxidative stress in the skin: Impact and related protection

Skin, our first interface to the external environment, is subjected to oxidative stress caused by a variety of factors such as solar ultraviolet, infrared and visible light, environmental pollution, including ozone and particulate matters, and psychological stress. Excessive reactive species, including reactive oxygen species and reactive nitrogen species, exacerbate skin pigmentation and aging, which further lead to skin tone unevenness, pigmentary disorder, skin roughness and wrinkles. Besides these, skin microbiota are also a very important factor ensuring the proper functions of skin. While environmental factors such as UV and pollutants impact skin microbiota compositions, skin dysbiosis results in various skin conditions. In this review, we summarize the generation of oxidative stress from exogenous and endogenous sources. We further introduce current knowledge on the possible roles of oxidative stress in skin pigmentation and aging, specifically with emphasis on oxidative stress and skin pigmentation. Meanwhile, we summarize the science and rationale of using three well-known antioxidants, namely vitamin C, resveratrol and ferulic acid, in the treatment of hyperpigmentation. Finally, we discuss the strategy for preventing oxidative stress-induced skin pigmentation and aging.

Long-Term Course of Polymorphic Light Eruption: A Registry Analysis

Background: Little is known about the long-term course of polymorphic light eruption (PLE).

Objective: To predict disease course, a questionnaire was sent to patients whose PLE had been diagnosed between March 1990 and December 2018 and documented in the Austrian Cooperative Registry for Photodermatoses.

Methods: In January 2019, 205 PLE patients were contacted by mail and asked to complete a questionnaire on their disease course, including whether the skin's sun sensitivity had normalized (i.e., PLE symptoms had disappeared), improved, stayed the same, or worsened over time. Patients who reported normalization of sun sensitivity were asked to report when it had occurred.

Results: Ninety-seven patients (79 females, 18 males) returned a completed questionnaire. The mean (range) duration of follow-up from PLE onset was 29.6 (17–54) years for females and 29.4 (16–47) years for males. The disease disappeared in 32 (41%) females after 17.4 (2–41) years and in 4 (24%) males after 11.8 (5–26) years. Twenty-nine (37%) females and 6 (35%) males reported improvement of symptoms over time; 15 females (19%) and 7 males (41%) reported no change; and 3 females (4%) and no males reported worsening of symptoms. Kaplan-Meier analysis revealed that after 20 years 74% (95%CI, 64–82%) of patients still suffered from PLE. PLE lesion persistence (>1 week) tended to predict a prolonged course of PLE.

Conclusions: PLE usually takes a long-term course over many years though in most patients its symptoms improve or disappear over time. How improvement relates to the pathophysiology of the disease remains to be determined.

Propionic acid produced by Cutibacterium acnes fermentation ameliorates ultraviolet B-induced melanin synthesis

Ultraviolet irradiation induces melanin accumulation, which can be reduced by the use of chemical whitening products. However, the associated safety concerns of such products have prompted the search for natural and harmless alternatives. This study aimed to identify a natural acidic formulation to reduce skin pigmentation. The metabolite propionic acid (CH3CH2COOH, PA) was the most abundant fatty acid in the filtrate from Pluronic F68 (PF68) fermentation of Cutibacterium acnes (C. acnes) and reduced the DOPA-positive melanocytes by significantly inhibiting cellular tyrosinase activity via binding to the free fatty acid receptor 2 (FFAR2). Moreover, 4 mM PA treatment did not alter melanocyte proliferation, indicating that it is an effective solution for hyperpigmentation, causing no cellular damage. The reduced DOPA-positive melanocytes and tyrosinase activity were also observed in mice ear skin tissue injected with a mixture of C. acnes and PF68, supporting that the inhibition of melanogenesis is likely to be mediated through fermentation metabolites from C. acnes fermentation using PF68 as a carbon source. Additionally, PA did not affect the growth of its parent bacteria C. acnes, hence is a potent fermentation metabolite that does not disrupt the balance of the skin microbiome.

Adult skin acute stress responses to short-term environmental and internal aggression from exposome factors

Exposome factors that lead to stressed skin can be defined as any disturbance to homeostasis from environmental (meteorological factors, solar radiation, pollution or tobacco smoke) and/or internal exposure (unhealthy diet, hormonal variations, lack of sleep, psychosocial stress). The clinical and biological impact of chronic exposome effects on skin functions has been extensively reviewed, whereas there is a paucity of information on the impact of short‐term acute exposure. Acute stress, which would typically last minutes to hours (and generally no more than a week), provokes a transient but robust neuroendocrine‐immune and tissue remodelling response in the skin and can alter the skin barrier. Firstly, we provide an overview of the biological effects of various acute stressors on six key skin functions, namely the skin physical barrier, pigmentation, defences (antioxidant, immune cell‐mediated, microbial and microbiome maintenance), structure (extracellular matrix and appendages), neuroendocrine and thermoregulation functions. Secondly, we describe the biological and clinical effects on adult skin from individual exposome factors that elicit an acute stress response and their consequences in skin health maintenance. Clinical manifestations of acutely stressed skin may include dry skin that might accentuate fine lines, oily skin, sensitive skin, pruritus, erythema, pale skin, sweating, oedema and flares of inflammatory skin conditions such as acne, rosacea, atopic dermatitis, pigmentation disorders and skin superinfection such as viral reactivation. Acute stresses can also induce scalp sensitivity, telogen effluvium and worsen alopecia.

The Role of the Environment and Exposome in Atopic Dermatitis

Purpose of review

Atopic dermatitis (AD) is a chronic inflammatory skin disorder affecting up to 20% of children and up to 5% of adults worldwide, contributing to significant disease-related morbidity in this patient cohort. Its aetiopathogenesis is underpinned by multiple factors, including genetic susceptibility, skin barrier defects, a skewed cutaneous immune response and microbiome perturbation in both the skin and the gut. In this review, we aim to examine the biological effects of key environmental exposures (the sum of which is termed the “exposome”) at the population, community and individual levels in order to describe their effect on AD pathogenesis.

Recent findings

It is now understood that as well as considering the type of environmental exposure with regard to its effect on AD pathogenesis, the dosage and timing of the exposure are both critical domains that may lead to either exacerbation or amelioration of disease. In this review, we consider the effects of population-wide exposures such as climate change, migration and urbanization; community-specific exposures such as air pollution, water hardness and allergic sensitisation; and individual factors such as diet, microbiome alteration, psychosocial stress and the impact of topical and systemic therapy.

Summary

This review summarises the interaction of the above environmental factors with the other domains of AD pathogenesis, namely, the inherent genetic defects, the skin barrier, the immune system and the cutaneous and gut microbiota. We specifically emphasise the timing and dosage of exposures and its effect on the cellular and molecular pathways implicated in AD.

Ultraviolet radiation, vitamin D, and COVID-19

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has become pandemic on March 11^th, 2020. COVID-19 has a range of symptoms that includes fever, fatigue, dry cough, aches, and labored breathing to acute respiratory distress and possibly death. Health systems and hospitals have been completely rearranged since March 2020 in order to limit the high rate of virus spreading. Hence, a great debate on deferrable visits and treatments including phototherapy for skin diseases is developing. In particular, as regards phototherapy very few data are currently available regarding the chance to continue it, even if it may be a useful resource for treating numerous dermatological patients. However, phototherapy has an immunosuppressive action possibly facilitating virus infection. In the context of COVID-19 infection risk it is important to pointed out whether sunlight, phototherapy and in particular ultraviolet radiation (UV-R) constitute or not a risk for patients. In this review we aimed to focus on the relationship between UV-R, sunlight, phototherapy, and viral infections particularly focusing on COVID-19.

Challenging Cosmetic Innovation: The Skin Microbiota and Probiotics Protect the Skin from UV-Induced Damage

Many studies performed in the last decade have focused on the cutaneous microbiota. It has been shown that this microbiota plays a key role in skin homeostasis. Considered as “a second barrier” to the environment, it is very important to know how it reacts to exogenous aggressions. The cosmetics industry has a started to use this microbiota as a source of natural ingredients, particularly ones that confer photoprotection against ultraviolet (UV) rays. Interestingly, it has been demonstrated that bacterial molecules can block UV rays or reverse their harmful effects. Oral probiotics containing living microorganisms have also shown promising results in restoring skin homeostasis and reversing the negative effects of UV rays. Microbial-based active sunscreen compounds have huge potential for use as next-generation photoprotection products.

Human Skin Microbiome: Impact of Intrinsic and Extrinsic Factors on Skin Microbiota

The skin is the largest organ of the human body and it protects the body from the external environment. It has become the topic of interest of researchers from various scientific fields. Microorganisms ensure the proper functioning of the skin. Of great importance, are the mutual relations between such microorganisms and their responses to environmental impacts, as dysbiosis may contribute to serious skin diseases. Molecular methods, used for microorganism identification, allow us to gain a better understanding of the skin microbiome. The presented article contains the latest reports on the skin microbiota in health and disease. The review discusses the relationship between a properly functioning microbiome and the body's immune system, as well as the impact of internal and external factors on the human skin microbiome.

Role of Commensal Microbes in the γ-Ray Irradiation-Induced Physiological Changes in Drosophila melanogaster

Ionizing radiation induces biological/physiological changes and affects commensal microbes, but few studies have examined the relationship between the physiological changes induced by irradiation and commensal microbes. This study investigated the role of commensal microbes in the γ-ray irradiation-induced physiological changes in Drosophila melanogaster. The bacterial load was increased in 5 Gy irradiated flies, but irradiation decreased the number of operational taxonomic units. The mean lifespan of conventional flies showed no significant change by irradiation, whereas that of axenic flies was negatively correlated with the radiation dose. γ-Ray irradiation did not change the average number of eggs in both conventional and axenic flies. Locomotion of conventional flies was decreased after 5 Gy radiation exposure, whereas no significant change in locomotion activity was detected in axenic flies after irradiation. γ-Ray irradiation increased the generation of reactive oxygen species in both conventional and axenic flies, but the increase was higher in axenic flies. Similarly, the amounts of mitochondria were increased in irradiated axenic flies but not in conventional flies. These results suggest that axenic flies are more sensitive in their mitochondrial responses to radiation than conventional flies, and increased sensitivity leads to a reduced lifespan and other physiological changes in axenic flies.

A deep dive into UV-based phototherapy: Mechanisms of action and emerging molecular targets in inflammation and cancer

UV-based phototherapy (including psoralen plus UVA (PUVA), UVB and UVA1) has a long, successful history in the management of numerous cutaneous disorders. Photoresponsive diseases are etiologically diverse, but most involve disturbances in local (and occasionally systemic) inflammatory cells and/or abnormalities in keratinocytes that trigger inflammation. UV-based phototherapy works by regulating the inflammatory component and inducing apoptosis of pathogenic cells. This results in a fascinating and complex network of simultaneous events-immediate transcriptional changes in keratinocytes, immune cells, and pigment cells; the emergence of apoptotic bodies; and the trafficking of antigen-presenting cells in skin-that quickly transform the microenvironment of UV-exposed skin. Molecular elements in this system of UV recognition and response include chromophores, metabolic byproducts, innate immune receptors, neurotransmitters and mediators such as chemokines and cytokines, antimicrobial peptides, and platelet activating factor (PAF) and PAF-like molecules that simultaneously shape the immunomodulatory effects of UV and their interplay with the microbiota of the skin and beyond. Phototherapy's key effects-proapoptotic, immunomodulatory, antipruritic, antifibrotic, propigmentary, and pro-prebiotic-promote clinical improvement in various skin diseases such as psoriasis, atopic dermatitis (AD), graft-versus-host disease (GvHD), vitiligo, scleroderma, and cutaneous T-cell lymphoma (CTCL) as well as prevention of polymorphic light eruption (PLE). As understanding of phototherapy improves, new therapies (UV- and non-UV-based) are being developed that will modify regulatory T-cells (Treg), interact with (resident) memory T-cells and /or utilize agonists and antagonists as well as antibodies targeting soluble molecules such as cytokines and chemokines, transcription factors, and a variety of membrane-associated receptors.

Hydroa Vacciniforme and Hydroa Vacciniforme-Like Lymphoproliferative Disorder: A Spectrum of Disease Phenotypes Associated with Ultraviolet Irradiation and Chronic Epstein-Barr Virus Infection

Hydroa vacciniforme (HV) is a rare form of photosensitivity disorder in children and is frequently associated with Epstein–Barr virus (EBV) infection, whereas HV-like lymphoproliferative disorders (HVLPD) describe a spectrum of EBV-associated T-cell or natural killer (NK)-cell lymphoproliferations with HV-like cutaneous manifestations, including EBV-positive HV, atypical HV, and HV-like lymphoma. Classic HV occurs in childhood with papulovesicules on sun-exposed areas, which is usually induced by sunlight and ultraviolet irradiation, and mostly resolves by early adult life. Unlike classic HV, atypical or severe HV manifests itself as recurrent papulovesicular eruptions in sun-exposed and sun-protected areas associated occasionally with facial edema, fever, lymphadenopathy, oculomucosal lesions, gastrointestinal involvement, and hepatosplenomegaly. Notably, atypical or severe HV may progress to EBV-associated systemic T-cell or natural killer (NK)-cell lymphoma after a chronic course. Although rare in the United States and Europe, atypical or severe HV and HV-like lymphoma are predominantly reported in children from Asia and Latin America with high EBV DNA levels, low numbers of NK cells, and T cell clones in the blood. In comparison with the conservative treatment used for patients with classic HV, systemic therapy such as immunomodulatory agents is recommended as the first-line therapy for patients with atypical or severe HV. This review aims to provide an integrated overview of current evidence and knowledge of HV and HVLPD to elucidate the pathophysiology, practical issues, environmental factors, and the impact of EBV infection.

Understanding building-occupant-microbiome interactions toward healthy built environments: A review

Built environments, occupants, and microbiomes constitute a system of ecosystems with extensive interactions that impact one another. Understanding the interactions between these systems is essential to develop strategies for effective management of the built environment and its inhabitants to enhance public health and well-being. Numerous studies have been conducted to characterize the microbiomes of the built environment. This review summarizes current progress in understanding the interactions between attributes of built environments and occupant behaviors that shape the structure and dynamics of indoor microbial communities. In addition, this review also discusses the challenges and future research needs in the field of microbiomes of the built environment that necessitate research beyond the basic characterization of microbiomes in order to gain an understanding of the causal mechanisms between the built environment, occupants, and microbiomes, which will provide a knowledge base for the development of transformative intervention strategies toward healthy built environments. The pressing need to control the transmission of SARS-CoV-2 in indoor environments highlights the urgency and significance of understanding the complex interactions between the built environment, occupants, and microbiomes, which is the focus of this review.

Extrinsic Factors Shaping the Skin Microbiome

Human skin, our most environmentally exposed organ, is colonized by a vast array of microorganisms constituting its microbiome. These bacterial communities are crucial for the fulfillment of human physiological functions such as immune system modulation and epidermal development and differentiation. The structure of the human skin microbiome is established during the early life stages, starting even before birth, and continues to be modulated throughout the entire life cycle, by multiple host-related and environmental factors. This review focuses on extrinsic factors, ranging from cosmetics to the environment and antibacterial agents, as forces that impact the human skin microbiome and well-being. Assessing the impact of these factors on the skin microbiome will help elucidate the forces that shape the microbial populations we coexist with. Furthermore, we will gain additional insight into their tendency to stimulate a healthy environment or to increase the propensity for skin disorder development.

Changes of the human skin microbiota upon chronic exposure to polycyclic aromatic hydrocarbon pollutants

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are of environmental and public health concerns and contribute to adverse skin attributes such as premature skin aging and pigmentary disorder. However, little information is available on the potential roles of chronic urban PAH pollutant exposure on the cutaneous microbiota. Given the roles of the skin microbiota have on healthy and undesirable skin phenotypes and the relationships between PAHs and skin properties, we hypothesize that exposure of PAHs may be associated with changes in the cutaneous microbiota. In this study, the skin microbiota of over two hundred Chinese individuals from two cities in China with varying exposure levels of PAHs were characterized by bacterial and fungal amplicon and shotgun metagenomics sequencing.

RESULTS

Skin site and city were strong parameters in changing microbial communities and their assembly processes. Reductions of bacterial-fungal microbial network structural integrity and stability were associated with skin conditions (acne and dandruff). Multivariate analysis revealed associations between abundances of Propionibacterium and Malassezia with host properties and pollutant exposure levels. Shannon diversity increase was correlated to exposure levels of PAHs in a dose-dependent manner. Shotgun metagenomics analysis of samples (n = 32) from individuals of the lowest and highest exposure levels of PAHs further highlighted associations between the PAHs quantified and decrease in abundances of skin commensals and increase in oral bacteria. Functional analysis identified associations between levels of PAHs and abundance of microbial genes of metabolic and other pathways with potential importance in host-microbe interactions as well as degradation of aromatic compounds.

CONCLUSIONS

The results in this study demonstrated the changes in composition and functional capacities of the cutaneous microbiota associated with chronic exposure levels of PAHs. Findings from this study will aid the development of strategies to harness the microbiota in protecting the skin against pollutants. Video Abstract.

Assessment of the Microbiome Role in Skin Protection Against UV Irradiation Via Network Analysis

Introduction: Diverse microbiotas which have some contributions to gene expression reside in human skin. To identify the protective role of the skin microbiome against UV exposure, proteinprotein interaction (PPI) network analysis is used to assessment gene expression alteration. Methods: A microarray dataset, GEO accession number GSE117359, was considered in this respect. Differential expressed genes (DEGs) in the germ-free (GF) and specific pathogen-free (SPF) groups are analyzed by GEO2R. The top significant DEGs were assigned for network analysis via Cytoscape 3.7.2 and its applications. Results: A total of 28 genes were identified as significant DEGs and the centrality analysis of the network indicated that only one of the seven hub-bottlenecks was from queried genes. The gene ontology analysis of Il6, Cxcl2, Cxcl1, TNF, Il10, Cxcl10, and Mmp9 showed that the crucial genes were highly enriched in the immune system. Conclusion: The skin microbiome plays a significant role in the protection of skin against UV irradiation and the role of TNF and IL6 is prominent in this regard.

Our natural "makeup" reveals more than it hides: Modeling the skin and its microbiome

Skin is our primary interface with the environment. A structurally and functionally complex organ that hosts a dynamic ecosystem of microbes, and synthesizes many compounds that affect our well-being and psychosocial interactions. It is a natural platform of signal exchange between internal organs, skin resident microbes, and the environment. These interactions have gained a great deal of attention due to the increased prevalence of atopic diseases, and the co-occurrence of multiple allergic diseases related to allergic sensitization in early life. Despite significant advances in experimentally characterizing the skin, its microbial ecology, and disease phenotypes, high-levels of variability in these characteristics even for the same clinical phenotype are observed. Addressing this variability and resolving the relevant biological processes requires a systems approach. This review presents some of our current understanding of the skin, skin-immune, skin-neuroendocrine, skin-microbiome interactions, and computer-based modeling approaches to simulate this ecosystem in the context of health and disease. The review highlights the need for a systems-based understanding of this sophisticated ecosystem. This article is categorized under: Infectious Diseases > Computational Models.

How It Works: The Immunology Underlying Phototherapy

Phototherapeutic modalities induce apoptosis of keratinocytes and immune cells, impact cytokine production, downregulate the IL-23/Th17 axis, and induce regulatory T cells. As in anti-IL-17 or anti-IL-23 antibody treatment, the dual action of phototherapy on skin and the immune system is likely responsible for sustained resolution of lesions in diseases such as psoriasis. In cutaneous T cell lymphoma, phototherapy may function by causing tumor cell apoptosis and eliminating the neoplastic and inflammatory infiltrate. Further research on phototherapeutic mechanisms will help advance, optimize, and refine dermatologic treatments and may open up novel avenues for treatment strategies in dermatology and beyond.

Building upon current knowledge and techniques of indoor microbiology to construct the next era of theory into microorganisms, health, and the built environment

In the constructed habitat in which we spend up to 90% of our time, architectural design influences occupants' behavioral patterns, interactions with objects, surfaces, rituals, the outside environment, and each other. Within this built environment, human behavior and building design contribute to the accrual and dispersal of microorganisms; it is a collection of fomites that transfer microorganisms; reservoirs that collect biomass; structures that induce human or air movement patterns; and space types that encourage proximity or isolation between humans whose personal microbial clouds disperse cells into buildings. There have been recent calls to incorporate building microbiology into occupant health and exposure research and standards, yet the built environment is largely viewed as a repository for microorganisms which are to be eliminated, instead of a habitat which is inexorably linked to the microbial influences of building inhabitants. Health sectors have re-evaluated the role of microorganisms in health, incorporating microorganisms into prevention and treatment protocols, yet no paradigm shift has occurred with respect to microbiology of the built environment, despite calls to do so. Technological and logistical constraints often preclude our ability to link health outcomes to indoor microbiology, yet sufficient study exists to inform the theory and implementation of the next era of research and intervention in the built environment. This review presents built environment characteristics in relation to human health and disease, explores some of the current experimental strategies and interventions which explore health in the built environment, and discusses an emerging model for fostering indoor microbiology rather than fearing it.

Balance between Health Risks and Benefits for Outdoor Workers Exposed to Solar Radiation: An Overview on the Role of Near Infrared Radiation Alone and in Combination with Other Solar Spectral Bands

Near infrared or infrared A (IRA) accounts for over 40% of the solar spectrum (SS) and is able to reach subcutaneous tissue as well as the retina. Outdoor workers are occupationally exposed to solar radiation (SR), but the level of exposure may differ widely depending on the job performed, time spent outdoors, latitude, altitude, season, personal protection, etc. Until now, risk assessment and management for outdoor workers has focused on the prevention of both acute and long-term effects on the eye and the skin due to solar ultraviolet radiation (UVR) with little consideration of the other components of the SS (a possible exception is represented by visible radiation with reference to the eye). A growing body of evidence coming from in vitro studies indicates that IRA is involved in cellular reactive oxygen species (ROS) production and may interfere with the respiratory chain in the mitochondria. Moreover, it can modulate gene expression and some metabolic pathways. The biological action of IRA is only partly attributable to a thermal mechanism, should it be also involved in photochemical ones. The cellular and molecular pathways affected by IRA are partly similar and partly different with respect to those involved in the case of visible ultraviolet A (UVA) and ultraviolet B (UVB) radiation. Consequently, the net effect of the SS is very difficult to predict at different levels of the biological organization, making more difficult the final balance of health risk and benefits (for the skin, eye, immune system, blood pressure, etc.) in a given exposure situation. Moreover, few in vivo studies and no epidemiological data are presently available in this regard. Investigating this topic may contribute to better defining the individual exposome. More practically, it is expected to bring benefits to the risk assessment and management for outdoor workers exposed to SS, contributing to: (1) better definition of the individual profiles of susceptibility, (2) more focused preventive and protective measures, (3) better implementation of the health surveillance and (4) a more effective information and training.

Glycerol 85% efficacy on atopic skin and its microbiome: a randomized controlled trial with clinical and bacteriological evaluation

Background: Treating atopic dermatitis (AD) is still a challenge. The staphylococcal skin load is known to aggravate AD. Narrow band ultraviolet B (NB-UVB) and glycerol in low concentration (20-40%) are established therapies for AD. NB-UVB has proven antimicrobial actions, while high concentration glycerol (85-100%) showed similar effects in vitro but has not been clinically tested.Objective: To evaluate the efficacy and tolerability of concentrated glycerol 85% compared to NB-UVB in patients with AD, as assessed by clinical improvement and reduction of staphylococcal colonization of the skin.Methods: 30 patients with mild to moderate AD were randomized into either NB-UVB or glycerol 85% group. Patients were treated for one month and followed for an additional month. Swabs were taken from the skin and nose to be cultured on mannitol-salt agar for Staphylococci and quantified to determine Colony Forming Units.Results: Both groups showed statistically insignificant microbial changes and statistically significant clinical improvement after treatment. The results were comparable between both groups.Conclusions: Concentrated glycerol 85% is a cheap effective readily accessible alternative for phototherapy in patients with mild-moderate AD who cannot access the facility. Reduction of staphylococcal skin load seems to be involved, but its role is minimal.

Revealing the secret life of skin - with the microbiome you never walk alone

The human skin microbiome has recently become a focus for both the dermatological and cosmetic fields. Understanding the skin microbiota, that is the collection of vital microorganisms living on our skin, and how to maintain its delicate balance is an essential step to gain insight into the mechanisms responsible for healthy skin and its appearance. Imbalances in the skin microbiota composition (dysbiosis) are associated with several skin conditions, either pathological such as eczema, acne, allergies or dandruff or non‐pathological such as sensitive skin, irritated skin or dry skin. Therefore, the development of approaches which preserve or restore the natural, individual balance of the microbiota represents a novel target not only for dermatologists but also for skincare applications. This review gives an overview on the current knowledge on the skin microbiome, the currently available sampling and analysis techniques as well as a description of current approaches undertaken in the skincare segment to help restoring and balancing the structure and functionality of the skin microbiota.

Plant-Microbe Interactions Facing Environmental Challenge

In the past four decades, tremendous progress has been made in understanding how plants respond to microbial colonization and how microbial pathogens and symbionts reprogram plant cellular processes. In contrast, our knowledge of how environmental conditions impact plant-microbe interactions is less understood at the mechanistic level, as most molecular studies are performed under simple and static laboratory conditions. In this review, we highlight research that begins to shed light on the mechanisms by which environmental conditions influence diverse plant-pathogen, plant-symbiont, and plant-microbiota interactions. There is a great need to increase efforts in this important area of research in order to reach a systems-level understanding of plant-microbe interactions that are more reflective of what occurs in nature.

The influence of treatment in alpine and moderate maritime climate on the composition of the skin microbiome in patients with difficult to treat atopic dermatitis

BACKGROUND

The skin microbiome, characterized by an overgrowth of Staphylococcus aureus, plays an important role in the pathogenesis of atopic dermatitis (AD). Multidisciplinary treatment in alpine climate is known for its positive effect on disease severity in children with AD and can result in a different immune response compared with moderate maritime climate. However, the effect on the composition of the skin microbiome in AD is unknown.

OBJECTIVE

To determine the effect of treatment in alpine climate and moderate maritime climate on the microbiome for lesional and non-lesional skin in children with difficult to treat AD.

RESULTS

Alpine climate treatment led to a significant change in the microbiota on lesional skin, whereas no significant change was found after moderate maritime climate. On both lesional and non-lesional skin, we observed a significant increase in Shannon diversity and a significant decrease in both Staphylococcus abundance and S aureus load after alpine climate treatment. The decrease in S aureus was significantly larger on lesional skin following alpine climate treatment compared with moderate maritime climate treatment. Staphylococcus epidermidis load was stable over time.

CONCLUSIONS AND CLINICAL RELEVANCE

Alpine climate treatment leads to significant changes in the composition of the skin microbiome in children with AD, mainly caused by a reduction in the Staphylococcus genus. This study shows new perspectives in the potential mode of action for therapies in AD.

Skin Microbiome Modulates the Effect of Ultraviolet Radiation on Cellular Response and Immune Function

The skin is colonized by a diverse microbiome intricately involved in various molecular and cellular processes within the skin and beyond. UV radiation is known to induce profound changes in the skin and modulate the immune response. However, the role of the microbiome in UV-induced immune suppression has been overlooked. By employing the standard model of contact hypersensitivity (using germ-free mice) we found diminished UV-induced systemic immune suppression in the presence of microbiome. Upon UV exposure, we found enhanced epidermal hyperplasia and neutrophilic infiltration in the presence and enhanced numbers of mast cells and monocyte or macrophages in the absence of microbiome. Transcriptome analysis revealed a predominant expression of cytokine genes related to pro-inflammatory milieu in the presence versus immunosuppressive milieu (with increased interleukin-10) in the absence of microbiome. Collectively, microbiome abrogates the immunosuppressive response to UV by modulating gene expression and cellular microenvironment of the skin.

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Epidermal and immune response to UV is dependent on skin microbiome

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Increased neutrophilic infiltration and expression of IL-1β in SPF mice after UV-R

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Elevated macrophage infiltration and expression of IL-10 in GF mice after UV-R

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Skin microbiome diminishes UV-induced immune suppression to contact allergen DNFB