Host/Malassezia Interaction: A Quantitative, Non-Invasive Method Profiling Oxylipin Production Associates Human Skin Eicosanoids with Malassezia

Life stage impact on the human skin ecosystem: lipids and the microbial community

Sebaceous free fatty acids are metabolized by multiple skin microbes into bioactive lipid mediators termed oxylipins. This study investigated correlations between skin oxylipins and microbes on the superficial skin of pre-pubescent children (N = 36) and adults (N = 100), including pre- (N = 25) and post-menopausal females (N = 25). Lipidomics and metagenomics revealed that Malassezia restricta positively correlated with the oxylipin 9,10-DiHOME on adult skin and negatively correlated with its precursor, 9,10-EpOME, on pre-pubescent skin. Co-culturing Malassezia with keratinocytes demonstrated a link between 9,10-DiHOME and pro-inflammatory cytokines IL-1β and IL-6 production. We also observed strong correlations between other skin oxylipins and microbial taxa, highlighting life stage differences in sebum production and microbial community composition. Our findings imply a complex host-microbe communication system mediated by lipid metabolism occurring on human skin, warranting further research into its role in skin health and disease and paving the way towards novel therapeutic targets and treatments.

A New Generation of Postbiotics for Skin and Scalp: In Situ Production of Lipid Metabolites by Malassezia

Effects of pre- and probiotics on intestinal health are well researched and microbiome-targeting solutions are commercially available. Even though a trend to appreciate the presence of certain microbes on the skin is seeing an increase in momentum, our understanding is limited as to whether the utilization of skin-resident microbes for beneficial effects holds the same potential as the targeted manipulation of the gut microflora. Here, we present a selection of molecular mechanisms of cross-communication between human skin and the skin microbial community and the impact of these interactions on the host's cutaneous health with implications for the development of skin cosmetic and therapeutic solutions. Malassezia yeasts, as the main fungal representatives of the skin microfloral community, interact with the human host skin via lipid mediators, of which several are characterized by exhibiting potent anti-inflammatory activities. This review therefore puts a spotlight on Malassezia and provides a comprehensive overview of the current state of knowledge about these fungal-derived lipid mediators and their capability to reduce aesthetical and sensory burdens, such as redness and itching, commonly associated with inflammatory skin conditions. Finally, several examples of current skin microbiome-based interventions for cosmetic solutions are discussed, and models are presented for the use of skin-resident microbes as endogenous bio-manufacturing platforms for the in situ supplementation of the skin with beneficial metabolites.

The facial microbiome and metabolome across different geographic regions

IMPORTANCE

Characterization of the skin microbiome and metabolome across geography will help uncover the climate factors behind the prevalence of skin disorders and provide suggestions for skincare products for people living in different geographic regions.

Current insights into skin lipids and their roles in cutaneous health and disease

PURPOSE OF REVIEW

The unique and complex array of cutaneous lipids include essential components of the skin structure and signalling molecules mediating homeostasis and inflammation. Understanding skin lipid biology and metabolism can support our comprehension of health and disease, including systemic conditions with cutaneous involvement.

RECENT FINDINGS

Lipids found on the skin surface, produced by both the host and resident microbes, maintain and regulate the skin microbiome and the epidermal barrier, whilst altered contributions from either source can be detrimental to skin health. The unique lipid composition of the epidermal barrier is essential for its function, and recent studies have expanded our understanding of epidermal ceramide production. This has been supported by improved models available for skin research, including organotypic skin models enabling in-vitro production of complex acylceramides for the first time, and model systems facilitating in-silico exploration of the lipid profile changes observed in clinical samples. Studies have revealed further involvement of lipid mediators such as eicosanoids in cutaneous inflammation, as well as immune regulation in both healthy and diseased skin.

SUMMARY

Skin lipids offer exciting opportunities as therapeutic targets for many conditions, whether through topical interventions or nutritional supplementation.

Fungal and bacterial oxylipins are signals for intra- and inter-cellular communication within plant disease

Lipids are central at various stages of host-pathogen interactions in determining virulence and modulating plant defense. Free fatty acids may act as substrates for oxidizing enzymes [e.g., lipoxygenases (LOXs) and dioxygenases (DOXs)] that synthesize oxylipins. Fatty acids and oxylipins function as modulators of several pathways in cell-to-cell communication; their structural similarity among plant, fungal, and bacterial taxa suggests potential in cross-kingdom communication. We provide a prospect of the known role of fatty acids and oxylipins in fungi and bacteria during plant-pathogen interactions. In the pathogens, oxylipin-mediated signaling pathways are crucial both in development and host infection. Here, we report on case studies suggesting that oxylipins derived from oleic, linoleic, and linolenic acids are crucial in modulating the pathogenic lifestyle in the host plant. Intriguingly, overlapping (fungi-plant/bacteria-plant) results suggest that different inter-kingdom pathosystems use similar lipid signals to reshape the lifestyle of the contenders and occasionally determine the outcome of the challenge.

Malassezia: A Commensal, Pathogen, and Mutualist of Human and Animal Skin

Identified in the late nineteenth century as a single species residing on human skin, Malassezia is now recognized as a diverse genus comprising 18 species inhabiting not only skin but human gut, hospital environments, and even deep-sea sponges. All cultivated Malassezia species are lipid dependent, having lost genes for lipid synthesis and carbohydrate metabolism. The surging interest in Malassezia results from development of tools to improve sampling, culture, identification, and genetic engineering, which has led to findings implicating it in numerous skin diseases, Crohn disease, and pancreatic cancer. However, it has become clear that Malassezia plays a multifaceted role in human health, with mutualistic activity in atopic dermatitis and a preventive effect against other skin infections due to its potential to compete with skin pathogens such as Candida auris. Improved understanding of complex microbe-microbe and host-microbe interactions will be required to define Malassezia's role in human and animal health and disease so as to design targeted interventions.

Many ways, one microorganism: Several approaches to study Malassezia in interactions with model hosts

Malassezia, a lipophilic and lipid-dependent yeast, is a microorganism of current interest to mycobiologists because of its role as a commensal or pathogen in health conditions such as dermatological diseases, fungemia, and, as discovered recently, cancer and certain neurological disorders. Various novel approaches in the study of Malassezia have led to increased knowledge of the cellular and molecular mechanisms of this yeast. However, additional efforts are needed for more comprehensive understanding of the behavior of Malassezia in interactions with the host. This article reviews advances useful in the experimental field for Malassezia.

Clinical lipidomics – A community-driven roadmap to translate research into clinical applications

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Overview of current state of mass spectrometry based lipidomics.

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Highlighting ongoing efforts towards harmonization.

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Invitation to join international community.

Lipid metabolites, beyond triglycerides and cholesterol, have been shown to have vast potential for applications in clinical applications, with substantial societal and economical value. To successfully evolve from the current research-grade methods to assays suitable for routine clinical applications, a harmonization – if not standardization – of these mass spectrometry-based workflows is necessary. Input on clinical needs and technological capabilities must be obtained from all relevant stakeholders, including wet lab scientists, informaticians and data scientists, manufacturers, and medical professionals. In order to build bridges between this diverse group of professionals, the International Lipidomics Society and its Clinical Lipidomics Interest Group were created. This opinion article is intended to provide an overview of international efforts to tackle the issues of workflow harmonization, and to serve as an open invitation for others to join this growing community.