Malassezia Yeast and Cytokine Gene Polymorphism in Atopic Dermatitis

Malassezia Globosa Aggravates Atopic Dermatitis by Influencing the Th1/Th2 Related Cytokines in Mouse Models

Purpose

To establish atopic dermatitis (AD) mouse models infected with Malassezia globosa and study its effects and potential mechanisms.

Methods

Twenty - four male BALB/c mice were randomly allocated into four groups: control, AD, M (normal mice treated with olive oil fungus suspension), and AD + M (AD mice treated with the same suspension). DNFB was used to induce the AD model. The M and AD + M groups were treated with Malassezia suspension. Body weight, scratching behavior, and skin lesion scores of mice were recorded. Skin tissues underwent HE and PAS staining, viable fungal flora counting, and Th1/Th2 cytokine detection via flow cytometry.

Results

The AD mouse models infected with Malassezia globosa were successfully set up. The AD + M group scratched more often. On days 8, 12, and 16, the AD group's skin lesion scores were (9.00±0.89), (10.17±0.87), (9.17±0.75), while those of the AD + M group were (11.00±0.82), (10.83±0.75), (10.83±0.75) (P<0.05). The AD + M group had more Malassezia colonization (P<0.001). The M group displayed a Th1 response. The AD + M group enhanced Th1 response and increased Th2 cytokines like IL - 4 and IL - 10 (P<0.05). The control group had normal skin with minimal scratching and low fungal counts.

Conclusion

Malassezia causes inflammation in normal and AD - like skin, with worse inflammation when the skin barrier is damaged. Targeting Malassezia might alleviate AD inflammation, offering new AD treatment directions.

From Skin and Gut to the Brain: The Infectious Journey of the Human Commensal Fungus Malassezia and Its Neurological Consequences

The human mycobiome encompasses diverse communities of fungal organisms residing within the body and has emerged as a critical player in shaping health and disease. While extensive research has focused on the skin and gut mycobiome, recent investigations have pointed toward the potential role of fungal organisms in neurological disorders. Among those fungal organisms, the presence of the commensal fungus Malassezia in the brain has created curiosity because of its commensal nature and primary association with the human skin and gut. This budding yeast is responsible for several diseases, such as Seborrheic dermatitis, Atopic dermatitis, Pityriasis versicolor, Malassezia folliculitis, dandruff, and others. However recent findings surprisingly show the presence of Malassezia DNA in the brain and have been linked to diseases like Alzheimer's disease, Parkinson's disease, Multiple sclerosis, and Amyotrophic lateral sclerosis. The exact role of Malassezia in these disorders is unknown, but its ability to infect human cells, travel through the bloodstream, cross the blood-brain barrier, and reside along with the lipid-rich neuronal cells are potential mechanisms responsible for pathogenesis. This also includes the induction of pro-inflammatory cytokines, disruption of the blood-brain barrier, gut-microbe interaction, and accumulation of metabolic changes in the brain environment. In this review, we discuss these key findings from studies linking Malassezia to neurological disorders, emphasizing the complex and multifaceted nature of these cases. Furthermore, we discuss potential mechanisms through which Malassezia might contribute to the development of neurological conditions. Future investigations will open up new avenues for our understanding of the fungal gut-brain axis and how it influences human behavior. Collaborative research efforts among microbiologists, neuroscientists, immunologists, and clinicians hold promise for unraveling the enigmatic connections between human commensal Malassezia and neurological disorders.

Fungal Head and Neck Dermatitis: Current Understanding and Management

Head and neck dermatitis (HND) is a form of atopic dermatitis (AD) that affects the seborrheic areas of the body and causes greater quality of life detriments than other types of AD. HND can be challenging to treat since first-line topical therapies may be ineffective or intolerable for long-term use on areas affected by HND while dupilumab may cause dupilumab-associated HND (DAHND). Current evidence implicates fungi, particularly Malassezia spp., in the pathogenesis of HND. Penetration of fungal antigens through the defective AD skin barrier activates the innate and adaptive immune systems to cause cutaneous inflammation via the T helper (Th)17 and/or Th2 axes. Malassezia sensitization may distinguish HND from other forms of AD. Multiple double-blind, placebo-controlled trials have shown antifungals to benefit HND, yet the persistence of symptom relief with sustained use remains unclear. Oral antifungals appear more effective than topical antifungals but may be harmful with long-term use. DAHND may also be fungal-mediated given improvement with antifungals and evidence of an overactive immune response against Malassezia in these patients. Janus kinase inhibitors are effective for HND, including DAHND, but may cause significant side effects when administered systemically. OX40/OX40L inhibitors and tralokinumab may be promising options for HND on the horizon. Demographic and environmental factors influence the host mycobiome and should be considered in future precision-medicine approaches as microbiome composition and diversity are linked to severity of HND.

Part 2: Understanding the role of Malassezia spp. in skin disorders: pathogenesis of Malassezia associated skin infections

INTRODUCTION

Malassezia is a major component of the skin microbiome, a lipophilic symbiotic organism of the mammalian skin, which can switch to opportunistic pathogens triggering multiple dermatological disorders in humans and animals. This phenomenon is favored by endogenous and exogenous host predisposing factors, which may switch Malassezia from a commensal to a pathogenic phenotype.

AREA COVERED

This review summarizes and discusses the most recent literature on the pathogenesis of Malassezia yeasts, which ultimately results in skin disorders with different clinical presentation. A literature search of Malassezia pathogenesis was performed via PubMed and Google scholar (up to May 2023), using the following keywords: Pathogenesis and Malassezia;host risk factors and Malassezia, Malassezia and skin disorders; Malassezia and virulence factors: Malassezia and metabolite production; Immunology and Malassezia.

EXPERT OPINION

Malassezia yeasts can maintain skin homeostasis being part of the cutaneous mycobiota; however, when the environmental or host conditions change, these yeasts are endowed with a remarkable plasticity and adaptation by modifying their metabolism and thus contributing to the appearance or aggravation of human and animal skin disorders.

Burden of Disease, Unmet Needs in the Diagnosis and Management of Atopic Dermatitis: An Indian Expert Consensus

Background

Atopic dermatitis (AD) is a chronic inflammatory, non-communicable, and relapsing skin disease that affects all age groups. There is a dearth of literature that reports the disease burden, and epidemiology and highlights unmet needs in the diagnosis and management of AD in India.

Methods

A total of ten specialists including dermatologists, pediatric dermatologists, and pediatricians with more than ten years of experience and practicing in different parts of India served as the expert panel during the virtual meet conducted on January 24, 2021. A questionnaire comprising 32 questions on different aspects of AD management was categorized among different sections: burden of disease (five questions), age of onset and prevalence (five questions), etiology and pathogenesis (six questions), diagnosis and severity of the disease (seven questions), and treatment (nine questions). Consensus was defined when agreement was provided by ≥90% of the experts.

Results

Considering the profound impact AD has on the quality of life (QoL) of patients, the expert panel recommended patient counseling while moderate to severe cases of AD need a prompt referral to a specialist. The panel did not recommend any specific diagnostic and severity criteria as a standard due to the inherent limitations associated with every criterion. The role of environment and changing lifestyle in addition to genetic and familial risk factors for AD was also considered. The panel unanimously recommended to conduct a countrywide, multicenter survey/study to estimate the true prevalence of AD in India. Further, the experts recommended to follow proper treatment protocols and to perform longitudinal monitoring for understanding corticosteroid treatment associated side effects.

Conclusion

This guidance focuses on identifying the unmet gaps and provides practical recommendations for improving QoL, diagnosis, prognosis, and overall management of patients with AD in India.

Cutaneous Malassezia: Commensal, Pathogen, or Protector?

The skin microbial community is a multifunctional ecosystem aiding prevention of infections from transient pathogens, maintenance of host immune homeostasis, and skin health. A better understanding of the complex milieu of microbe-microbe and host-microbe interactions will be required to define the ecosystem's optimal function and enable rational design of microbiome targeted interventions. Malassezia, a fungal genus currently comprising 18 species and numerous functionally distinct strains, are lipid-dependent basidiomycetous yeasts and integral components of the skin microbiome. The high proportion of Malassezia in the skin microbiome makes understanding their role in healthy and diseased skin crucial to development of functional skin health knowledge and understanding of normal, healthy skin homeostasis. Over the last decade, new tools for Malassezia culture, detection, and genetic manipulation have revealed not only the ubiquity of Malassezia on skin but new pathogenic roles in seborrheic dermatitis, psoriasis, Crohn's disease, and pancreatic ductal carcinoma. Application of these tools continues to peel back the layers of Malassezia/skin interactions, including clear examples of pathogenicity, commensalism, and potential protective or beneficial activities creating mutualism. Our increased understanding of host- and microbe-specific interactions should lead to identification of key factors that maintain skin in a state of healthy mutualism or, in turn, initiate pathogenic changes. These approaches are leading toward development of new therapeutic targets and treatment options. This review discusses recent developments that have expanded our understanding of Malassezia's role in the skin microbiome, with a focus on its multiple roles in health and disease as commensal, pathogen, and protector.

In Vitro or In Vivo Models, the Next Frontier for Unraveling Interactions between Malassezia spp. and Hosts. How Much Do We Know?

Malassezia is a lipid-dependent genus of yeasts known for being an important part of the skin mycobiota. These yeasts have been associated with the development of skin disorders and cataloged as a causal agent of systemic infections under specific conditions, making them opportunistic pathogens. Little is known about the host-microbe interactions of Malassezia spp., and unraveling this implies the implementation of infection models. In this mini review, we present different models that have been implemented in fungal infections studies with greater attention to Malassezia spp. infections. These models range from in vitro (cell cultures and ex vivo tissue), to in vivo (murine models, rabbits, guinea pigs, insects, nematodes, and amoebas). We additionally highlight the alternative models that reduce the use of mammals as model organisms, which have been gaining importance in the study of fungal host-microbe interactions. This is due to the fact that these systems have been shown to have reliable results, which correlate with those obtained from mammalian models. Examples of alternative models are Caenorhabditis elegans, Drosophila melanogaster, Tenebrio molitor, and Galleria mellonella. These are invertebrates that have been implemented in the study of Malassezia spp. infections in order to identify differences in virulence between Malassezia species.

Genetic relationship between IL-10 gene polymorphisms and the risk of clinical atopic dermatitis

Background

We retrieved different reports containing different genetic effects of − 1082 A/G, − 819 T/C, and − 592 A/C polymorphisms within the IL-10 (interleukin-10) gene on the susceptibility to clinical atopic dermatitis.

Methods

Herein, we conducted a meta-analysis to comprehensively assess such a genetic relationship after collecting the available published evidence. STATA 12.0 software was used for the statistical analysis under the allelic, homozygotic, heterozygotic, dominant, recessive and carrier genetic models.

Results

By retrieving and screening database literature, a total of 16 eligible case-control studies were finally selected. For the IL-10 -1082 A/G polymorphism, we did not detect a significant difference between atopic dermatitis cases and population-based controls in the overall meta-analysis under the genetic models of allele G vs. A (P = 0.540), GG vs. AA (P = 0.853), AG vs AA (P = 0.265), AG + GG vs AA (P = 0.221), GG vs AA+AG (P = 0.540) and carrier G vs. A (P = 0.643). Moreover, a statistically non-significant association was observed in the most subgroup meta-analyses by the factors of ethnicity, country and Hardy-Weinberg equilibrium. Likewise, the negative results were detected for the synthetic analysis of IL-10 -819 T/C and − 592 C/A polymorphisms.

Conclusion

The current evidence does not support a strong genetic relationship between IL-10 -1082 A/G, − 819 T/C and − 592 A/C polymorphisms and the susceptibility to atopic dermatitis.

Electronic supplementary material

The online version of this article (10.1186/s12881-019-0817-8) contains supplementary material, which is available to authorized users.