Epigenetic Regulation of Filaggrin Gene Expression in Human Epidermal Keratinocytes

Maternal tobacco exposure during pregnancy and atopic dermatitis in offspring: A systematic review and meta-analysis

The main purpose of this review was to examine the evidence of the relationship between active smoking or passive smoking during pregnancy and atopic dermatitis in offspring. The protocol was written following the PRISMA Checklist and was registered in the PROSPERO database (registration number CRD42022381136). We implemented a comprehensive search in PubMed, Embase and Web of Science databases to identify all potentially related articles from inception through 1 December 2022. We assessed cohort studies and case-control studies using the Newcastle-Ottawa Scale (NOS), and the Joanna Briggs Institute (JBI) critical appraisal tool to assess the quality of cross-sectional studies. Heterogeneity was investigated by using Cochrane Q tests and I2 statistics. In addition, according to the research design, population source and population size, the reasons for the heterogeneity were analysed. A total of 15 observational studies were included in this analysis. Our meta-analysis suggests that atopic dermatitis in offspring is not associated with active smoking during pregnancy (pooled OR, 0.96 [95% CI 0.86-1.07]); however, it is related to passive smoking (OR, 1.52 [95% CI 1.36-1.70]). Passive smoking during pregnancy is associated with an increased risk of eczema development in offspring. More research is needed to explore the risk of active smoking and eczema development in offspring, especially the association between measurements of pregnancy cotinine levels in maternal body fluids and AD in offspring.

Effect of Staphylococcus aureus colonization and immune defects on the pathogenesis of atopic dermatitis

Atopic dermatitis (AD) is a common and recurrent skin disease characterized by skin barrier dysfunction, inflammation and chronic pruritus, with wide heterogeneity in terms of age of onset, clinical course and persistence over the lifespan. Although the pathogenesis of the disease are unclear, epidermal barrier dysfunction, immune and microbial dysregulation, and environmental factors are known to be critical etiologies in AD pathology. The skin microbiota represents an ecosystem consisting of numerous microbial species that interact with each other as well as host epithelial cells and immune cells. Although the skin microbiota benefits the host by supporting the basic functions of the skin and preventing the colonization of pathogens, disruption of the microbial balance (dysbiosis) can cause skin diseases such as AD. Although AD is a dermatological disease, recent evidence has shown that changes in microbiota composition in the skin and intestine contribute to the pathogenesis of AD. Environmental factors that contribute to skin barrier dysfunction and microbial dysbiosis in AD include allergens, diet, irritants, air pollution, epigenetics and microbial exposure. Knowing the microbial combination of intestin, as well as the genetic and epigenetic determinants associated with the development of autoantibodies, may help elucidate the pathophysiology of the disease. The skin of patients with AD is characterized by microbial dysbiosis as a result of reduced microbial diversity and overgrowth of the pathogens such as Staphylococcus aureus. Recent studies have revealed the importance of building a strong immune response against microorganisms during childhood and new mechanisms of microbial community dynamics in modulating the skin microbiome. Numerous microorganisms are reported to modulate host response through communication with keratinocytes, specific immune cells and adipocytes to improve skin health and barrier function. This growing insight into bioactive substances in the skin microbiota has led to novel biotherapeutic approaches targeting the skin surface for the treatment of AD. This review will provide an updated overview of the skin microbiota in AD and its complex interaction with immune response mechanisms, as well as explore possible underlying mechanisms in the pathogenesis of AD and provide insights into new therapeutic developments for the treatment of AD. It also focuses on restoring skin microbial homeostasis, aiming to reduce inflammation by repairing the skin barrier.

Integrating multi-omics approaches in deciphering atopic dermatitis pathogenesis and future therapeutic directions

Atopic dermatitis (AD), a complex and heterogeneous chronic inflammatory skin disorder, manifests in a spectrum of clinical subtypes. The application of genomics has elucidated the role of genetic variations in predisposing individuals to AD. Transcriptomics, analyzing gene expression alterations, sheds light on the molecular underpinnings of AD. Proteomics explores the involvement of proteins in AD pathophysiology, while epigenomics examines the impact of environmental factors on gene expression. Lipidomics, which investigates lipid profiles, enhances our understanding of skin barrier functionalities and their perturbations in AD. This review synthesizes insights from these omics approaches, highlighting their collective importance in unraveling the intricate pathogenesis of AD. The review culminates by projecting future trajectories in AD research, particularly the promise of multi-omics in forging personalized medicine and novel therapeutic interventions. Such an integrated multi-omics strategy is poised to transform AD comprehension and management, steering towards more precise and efficacious treatment modalities.

The Role of Collagens in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease affecting both children and adults. The clinical picture of AD manifests in typical skin lesions, such as localized eczema and dry skin, with dominant, persistent itching that leads to sleep disturbances. The pathophysiology of AD has been extensively investigated with respect to epigenetic and genetic factors, skin barrier defects, as well as immunological and microbial disorders. However, to date, the involvement of extracellular matrix (ECM) elements has received limited attention. Collagen, a major component of the ECM, may serve as a therapeutic target for the future treatment of AD. This paper summarizes the role of collagens, which are the most abundant components of the extracellular matrix in AD.

Epigenetic control of inflammation in Atopic Dermatitis

Atopic dermatitis (AD), also known as atopic eczema, is a common but also complex chronic, itchy skin condition with underlying inflammation of the skin. This skin ailment is prevalent worldwide and affects people of all ages, particularly children below five years of age. The itching and resulting rashes in AD patients are often the result of inflammatory signals, thus necessitating a closer look at the inflammation-regulating mechanisms for putative relief, care and therapy. Several chemical- as well as genetically-induced animal models have established the importance of targeting pro-inflammatory AD microenvironment. Epigenetic mechanisms are gaining attention towards a better understanding of the onset as well as the progression of inflammation. Several physiological processes with implications in pathophysiology of AD, such as, barrier dysfunction either due to reduced filaggrin / human β-defensins or altered microbiome, reprograming of Fc receptors with resulting overexpression of high affinity IgE receptors, elevated eosinophil numbers or the elevated IL-22 production by CD4 + T cells have underlying epigenetic mechanisms that include differential promoter methylation and/or regulation by non-coding RNAs. Reversing these epigenetic changes has been verified to reduce inflammatory burden through altered secretion of cytokines IL-6, IL-4, IL-13, IL-17, IL-22 etc, with benefit against AD progression in experimental models. A thorough understanding of epigenetic remodeling of inflammation in AD has the potential of opening avenues for novel diagnostic, prognostic and therapeutic options.

Intrinsic Effects of Exposome in Atopic Dermatitis: Genomics, Epigenomics and Regulatory Layers

Atopic dermatitis (AD) or atopic eczema is an increasingly manifested inflammatory skin disorder of complex etiology which is modulated by both extrinsic and intrinsic factors. The exposome includes a person's lifetime exposures and their effects. We recently reviewed the extrinsic exposome's environmental risk factors that contribute to AD. The periods of pregnancy, infancy, and teenage years are recognized as crucial stages in the formation of AD, where the exposome leads to enduring impacts on the immune system. However, research is now focusing on the interactions between intrinsic pathways that are modulated by the extrinsic exposome, including genetic variation, epigenetic modifications, and signals, such as diet, stress, and microbiome interactions. As a result, immune dysregulation, barrier dysfunction, hormonal fluctuations, and skin microbiome dysbiosis are important factors contributing to AD development, and their in-depth understanding is crucial not only for AD treatment but also for similar inflammatory disorders.

Revisiting the Roles of Filaggrin in Atopic Dermatitis

The discovery in 2006 that loss-of-function mutations in the filaggrin gene (FLG) cause ichthyosis vulgaris and can predispose to atopic dermatitis (AD) galvanized the dermatology research community and shed new light on a skin protein that was first identified in 1981. However, although outstanding work has uncovered several key functions of filaggrin in epidermal homeostasis, a comprehensive understanding of how filaggrin deficiency contributes to AD is still incomplete, including details of the upstream factors that lead to the reduced amounts of filaggrin, regardless of genotype. In this review, we re-evaluate data focusing on the roles of filaggrin in the epidermis, as well as in AD. Filaggrin is important for alignment of keratin intermediate filaments, control of keratinocyte shape, and maintenance of epidermal texture via production of water-retaining molecules. Moreover, filaggrin deficiency leads to cellular abnormalities in keratinocytes and induces subtle epidermal barrier impairment that is sufficient enough to facilitate the ingress of certain exogenous molecules into the epidermis. However, although FLG null mutations regulate skin moisture in non-lesional AD skin, filaggrin deficiency per se does not lead to the neutralization of skin surface pH or to excessive transepidermal water loss in atopic skin. Separating facts from chaff regarding the functions of filaggrin in the epidermis is necessary for the design efficacious therapies to treat dry and atopic skin.

The Role of Collagen VI α6 Chain Gene in Atopic Dermatitis

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The Influence of Microbiome Dysbiosis and Bacterial Biofilms on Epidermal Barrier Function in Atopic Dermatitis-An Update

Atopic dermatitis (AD) is a common inflammatory dermatosis affecting up to 30% of children and 10% of adults worldwide. AD is primarily driven by an epidermal barrier defect which triggers immune dysregulation within the skin. According to recent research such phenomena are closely related to the microbial dysbiosis of the skin. There is growing evidence that cutaneous microbiota and bacterial biofilms negatively affect skin barrier function, contributing to the onset and exacerbation of AD. This review summarizes the latest data on the mechanisms leading to microbiome dysbiosis and biofilm formation in AD, and the influence of these phenomena on skin barrier function.

The Effects of Polymorphisms in One-carbon Metabolism Genes on Manifestation of Ichthyosis Vulgaris

BACKGROUND: Ichthyosis vulgaris is the most common type of Mendelian disorders of cornification, caused by loss-of-function mutations in the gene encoding epidermal protein filaggrin (FLG), namely R501X and 2282del4. FLG 2282del4 mutation in heterozygotes is incompletely penetrant. Polymorphisms in one-carbon metabolism genes could be associated with clinical manifestation of ichthyosis vulgaris. AIM: The purpose of the present study was to analyze the effects of MTHFR, MTR and MTRR polymorphisms in patients with ichthyosis vulgaris. METHODS: 31 patients with ichthyosis vulgaris, 7 their FLG heterozygous relatives without symptoms of disorder, and 150 healthy controls were enrolled in study. FLG null mutations —R501X (rs61816761) and 2282del4 (rs558269137) — and one-carbon metabolism gene polymorphisms — MTHFR C677T (rs1801133), MTHFR A1298C (rs1801131), MTR A2756G (rs1805087) and MTRR A66G (rs1801394) — were analyzed by a polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) assay. RESULTS: Among patients with ichthyosis, heterozygous for FLG 2282del4 mutation, the distributions of genotypes for folate metabolism genes were: MTHFR C677T CC:CT:TT —29.4%:70.6%:0.0%; MTHFR A1298C AA:AC:CC — 52.9%:47.1%:0.0%; MTR A2756G AA:AG:GG — 70.3%:23.5%:5.9%; MTRR A66G AA:AG:GG — 23.4%:52.9%:23.5%. The frequencies of MTR 2756AA and MTRR 66GG genotypes were 1.4–1.6 times higher in affected individuals heterozygous for 2282del4 than in patients with other FLG genotypes. In affected 2282del4 heterozygotes, the frequency of MTR 2756AA genotype was 1.6 times greater than in healthy controls (p<0.01). The strongest association was found between MTHFR 677CT/MTHFR 1298AA/MTR 2756AA/MTRR 66AG genotype and ichthyosis — OR=11.23 (95% CI 2.51−50.21, p=0.002). CONCLUSIONS: Various genotypes of one-carbon metabolism genes increase the risk of ichthyosis in heterozygotes for the FLG 2282del4 mutation (OR 2.799‑11.231). The most probable predisposing genotype is 677CT/1298AA/2756AA+AG/66AG.