The epithelial immune microenvironment (EIME) in atopic dermatitis and psoriasis

Downregulation of RSAD2 ameliorates keratinocyte hyperproliferation and skin inflammation in psoriasis via the TAK1/NF-κB axis

Immune cell infiltration and keratinocyte (KC) hyperproliferation are characteristics of psoriasis. Radical S-adenosyl methionine domain-containing 2 (RSAD2) plays an integral role in the innate immune response and is associated with various immune-related diseases. However, RSAD2's expression and role in modulating immune responses in psoriasis remain unexplored. In this study, we demonstrated a significant upregulation of RSAD2 expression in both psoriatic lesions and psoriasis-like mouse epidermis, with its expression positively correlated with psoriasis severity. In psoriatic cell models, RSAD2 was shown to promote the proliferation and secretion of pro-inflammatory cytokines by activating the transforming growth factor-β-activated kinase 1 (TAK1)-mediated nuclear factor kappa-B (NF-κB) signaling pathway. Additionally, it was found that the expression of RSAD2 is increased by the action of interferon regulatory factor-1 (IRF1), which binds to the promoter region of RSAD2. Therefore, the function of RSAD2 in psoriasis is regulated by IRF1. Notably, RSAD2 inhibition decreased epidermal hyperplasia and alleviated imiquimod (IMQ)-induced psoriatic dermatitis. In summary, our study highlights the modulation of the IRF1-RSAD2-TAK1 axis as a potential innovative therapeutic approach for psoriasis, offering new insights into the molecular mechanisms by which KCs drive inflammation in psoriasis.

Comparative Whole Metagenome Analysis in Lesional and Nonlesional Scalp Areas of Patients with Psoriasis Capitis and Healthy Individuals

Psoriasis is an immune-mediated inflammatory disorder, where the majority of the patients suffer from psoriasis capitis or scalp psoriasis. Current therapeutics remain ineffective to treat scalp lesions. In this study, we present a whole-metagenome characterization of the scalp microbiome in psoriasis capitis. We investigated how changes in the homeostatic cutaneous microbiome correlate with the condition and identified metagenomic biomarkers (taxonomic, functional, virulence factors, antimicrobial resistance genes) that could partly explain its emergence. Within this study, 83 top and back scalp samples from healthy individuals and 64 lesional and nonlesional scalp samples from subjects with untreated psoriasis capitis were analyzed. Using qPCR targeting the 16S and 18S ribosomal RNA genes, we found a significant decrease in microbial load within scalp regions affected by psoriasis compared with that in their nonlesional counterparts. Metagenomic analysis revealed that psoriatic lesions displayed significant lower Cutibacterium species (including C. modestum, C. namnetense, C. granulosum, C. porci), along with an elevation in Staphylococcus aureus. A heightened relative presence of efflux pump protein-encoding genes was detected, suggesting potential antimicrobial resistance mechanisms. These mechanisms are known to specifically target human antimicrobial peptides (including cathelicidin LL-37), which are frequently encountered within psoriasis lesions. These shifts in microbial community dynamics may contribute to psoriasis disease pathogenesis.

Interleukin-37 promotes wound healing in diabetic mice by inhibiting the MAPK/NLRP3 pathway

AIMS/INTRODUCTION

Diabetic foot ulcer (DFU) is a prevalent complication of diabetes characterized by heightened inflammation and impaired wound-healing processes. Interleukin-37 (IL-37) is a natural suppressor of innate inflammation. Here, we aim to investigate the potential of IL-37 in enhancing the healing process of diabetic wounds.

MATERIALS AND METHODS

The skin samples of DFU and non-diabetic patients during foot and ankle orthopedic surgery were collected. The IL-37 transgenic mice (IL-37Tg) were created using CRISPR/Cas-mediated genome engineering. Mice were administered streptozotocin (STZ, 150 mg/kg) to induce a diabetic model. After 4 weeks, an equidistant full-thickness excisional wound measuring 8 mm was created on the central back of each mouse and allowed to heal naturally. Body weight and blood glucose levels were measured weekly. The wound area was measured, and skin samples were collected on Day 10 for further Quantitative polymerase chain reaction (qPCR) and WB detection and RNA sequencing analysis.

RESULTS

The proinflammation cytokines such as TNF-α and IL-1β and the MAPK signaling pathway were significantly increased in the wound margin of DFU patients. Compared with diabetic mice, diabetic IL-37Tg mice showed a significantly accelerated healing process. The enriched signaling pathways in RNA sequencing included cytokine-cytokine receptor interaction, TNF signaling pathway, and NOD-like receptor signaling pathway. Through QPCR and WB detection, we found that IL-37 could inhibit the activated MAPK and NOD-like signaling pathway, reducing TNF-α, IL-1β, and NLRP3 expression in the diabetic wound.

CONCLUSIONS

IL-37 promotes skin wound healing in diabetic mice, providing a new possible target for treating diabetic wounds.

The AhR-Ovol1-Id1 regulatory axis in keratinocytes promotes epidermal and immune homeostasis in atopic dermatitis-like skin inflammation

The skin is our outer permeability and immune defense barrier against myriad external assaults. Aryl hydrocarbon receptor (AhR) senses environmental factors and regulates barrier robustness and immune homeostasis. AhR agonists have been approved by the FDA for psoriasis treatment and are in clinical trials for the treatment of atopic dermatitis (AD), but the underlying mechanism of action remains poorly defined. Here, we report that OVOL1/Ovol1 is a conserved and direct transcriptional target of AhR in epidermal keratinocytes. We show that OVOL1/Ovol1 influences AhR-mediated regulation of keratinocyte gene expression and that OVOL1/Ovol1 ablation in keratinocytes impairs the barrier-promoting function of AhR, exacerbating AD-like inflammation. Mechanistically, we have identified Ovol1's direct downstream targets genome-wide and provided in vivo evidence supporting the role of Id1 as a functional target in barrier maintenance, disease suppression, and neutrophil accumulation. Furthermore, our findings reveal that an IL-1/dermal γδT cell axis exacerbates type 2 and 3 immune responses downstream of barrier perturbation in Ovol1-deficient AD skin. Finally, we present data suggesting the clinical relevance of OVOL1 and ID1 functions in human AD skin. Our study highlights a keratinocyte-intrinsic AhR-Ovol1-Id1 regulatory axis that promotes both epidermal and immune homeostasis in the context of skin inflammation, identifying new therapeutic targets.

Type 2 immunity in allergic diseases

Significant advancements have been made in understanding the cellular and molecular mechanisms of type 2 immunity in allergic diseases such as asthma, allergic rhinitis, chronic rhinosinusitis, eosinophilic esophagitis (EoE), food and drug allergies, and atopic dermatitis (AD). Type 2 immunity has evolved to protect against parasitic diseases and toxins, plays a role in the expulsion of parasites and larvae from inner tissues to the lumen and outside the body, maintains microbe-rich skin and mucosal epithelial barriers and counterbalances the type 1 immune response and its destructive effects. During the development of a type 2 immune response, an innate immune response initiates starting from epithelial cells and innate lymphoid cells (ILCs), including dendritic cells and macrophages, and translates to adaptive T and B-cell immunity, particularly IgE antibody production. Eosinophils, mast cells and basophils have effects on effector functions. Cytokines from ILC2s and CD4+ helper type 2 (Th2) cells, CD8 + T cells, and NK-T cells, along with myeloid cells, including IL-4, IL-5, IL-9, and IL-13, initiate and sustain allergic inflammation via T cell cells, eosinophils, and ILC2s; promote IgE class switching; and open the epithelial barrier. Epithelial cell activation, alarmin release and barrier dysfunction are key in the development of not only allergic diseases but also many other systemic diseases. Recent biologics targeting the pathways and effector functions of IL4/IL13, IL-5, and IgE have shown promising results for almost all ages, although some patients with severe allergic diseases do not respond to these therapies, highlighting the unmet need for a more detailed and personalized approach.

Immune-Epithelial Cell Interactions during Epidermal Regeneration, Repair, and Inflammatory Diseases

The multiple layers of the skin cover and protect our entire body. Among the skin layers, the epidermis is in direct contact with the outer environment and serves as the first line of defense. The epidermis functions as a physical and immunological barrier. To maintain barrier function, the epidermis continually regenerates and repairs itself when injured. Interactions between tissue-resident immune cells and epithelial cells are essential to sustain epidermal regeneration and repair. In this review, we will dissect the crosstalk between epithelial cells and specific immune cell populations located in the epidermis during homeostasis and wound repair. In addition, we will analyze the contribution of dysregulated immune-epithelial interactions in chronic inflammatory diseases.

Quantitative lipidomics profiling of skin surface lipids and skin barrier function evaluation in patients with acne vulgaris

Sebum composition may be more important than amount for acne lesions, and current research on skin surface lipids (SSLs) focuses on determining their relative content. The objective of this study was to analyze the changes in the absolute content of SSLs in acne patients and their relationship with skin barrier function. To evaluate skin barrier function, transepidermal water loss (TEWL), skin moisture, sebum content, skin elasticity, and whiteness were measured, while SSL changes were investigated using LC-MS/MS. The results indicated that adult acne patients have reduced skin barrier function, as demonstrated by changes in skin moisture, sebum content, skin flexibility, and whitening. Notably, AGlcSiE, Cer, CL, Co, LPC, PA, PC, PE, PI, SM, So, SQDG, and TG were considerably enhanced in acne patients' SSLs, whereas CerG1, DG, DGDG, MGDG, PG, and phSM were decreased. Furthermore, side chain analysis showed that the ratio of linoleic acid to linolenic acid in acne patients' skin surface lipids was higher than in healthy controls, and the caprylic acid/capric acid ratio was likewise greater. The correlation study of SSLs and skin barrier function demonstrated that increasing LPC and decreasing PG are associated with skin barrier function deterioration. In conclusion, acne patients have compromised skin barrier function and altered SSL absolute content, and certain SSL species identified in this study could serve as potential targets for research into acne pathogenesis.

Reductive Adjuvant Nanosystem for Alleviated Atopic Dermatitis Syndromes

Atopic dermatitis (AD) is a recurrent and chronic inflammatory skin condition characterized by a high lifetime prevalence and significant impairment of patients' quality of life, primarily due to intense itching and discomfort. However, current pharmacological interventions provide only moderate efficacy and are frequently accompanied by adverse side effects. The immune-pathogenesis of AD involves dysregulation of the Th2 immune response and exacerbation of inflammation related to excessive reactive oxygen species (ROS). Therefore, to address these issues, in this study, we targeted the upstream pathogenesis by designing a pro-Th1 adjuvant nanoemulsion loaded with poly(I:C) and encapsulated with the ROS-scavenger vitamin E, termed PV-NE. PV-NE effectively rebalanced the Th1/Th2 immune response and reduced ROS levels both in vivo and ex vivo, leading to the restoration of immune balance in AD-affected skin and alleviation of symptoms such as lichenification and erythematous patches. In conclusion, our development of the reductive adjuvant nanosystem PV-NE demonstrates its biocompatibility and efficacy in combating AD progression without the use of immunosuppressant glucocorticoids. This has the potential to significantly impact the design and enhancement of pharmacotherapy in future clinical research aimed at curing AD.

Comparative Proteomics Analysis Reveals Distinct Molecular Phenotype and Biomarkers in Patients with Erythrodermic Atopic Dermatitis and Erythrodermic Psoriasis

Erythrodermic atopic dermatitis (EAD) and erythrodermic psoriasis (EP) are rare yet debilitating inflammatory skin disorders that propose challenges in diagnosis and discovering effective therapeutic targets. Despite their clinical and histological similarities, the underlying molecular mechanisms and systemic biomarkers of these diseases are substantially unclear. In this study, we sought to investigate the differential serum proteome of EP and EAD patients and identify biomarkers for these two subtypes of erythroderma. We recruited 14 EAD patients, 14 EP patients and 14 healthy controls. Serum samples were collected and analyzed using the Olink high-throughput platform to assess the levels of 269 inflammation-/immune response-/cardiovascular-related biomarkers. Both EAD and EP patients exhibited enhanced immune activation and dysregulated cardiovascular profiles compared to healthy controls. EAD demonstrated a more pronounced inflammation tone, characterized by Th1/Th2/Th22/IL-1-dominant patterns, as well as increased TNF superfamily, Th17, and apoptosis markers. Conversely, EP displayed inflammation with Th1/Th17/TNF-skewing and mild Th2 upregulation, along with notable increases in epidermal-development markers. Disease severity in EAD was strongly correlated with apoptosis/Th2 markers, while correlated with Th17 markers in EP. Furthermore, a panel of eight markers (IL-17A/IL-17C/PI3/CCL20/SH2D1A/SIRT2/DFFA/IL-13) was identified that effectively discriminated between EP and EAD, with an Area Under the Curve greater than 0.8. Our study comprehensively characterizes the circulating molecular profiles in EAD and EP patients, providing insights into the similarities and complexities of their inflammation phenotypes. The identified serum biomarkers have the potential to differentiate between EP and EAD, which could aid in the diagnosis and guiding tailored therapeutics.

Double-Layered Microneedle Patch Integrated with Multifunctional Nanoparticles and Live Bacteria for Long-Term Treatment of Atopic Dermatitis

Atopic dermatitis (AD) is a complex and prevalent chronic inflammatory skin disease that impacts a significant portion of the global population. Conventional treatments often focus on a singular pathogenic factor or suffer from limited skin penetration, resulting in unsatisfactory outcomes. Here, a multifunctional double-layered microneedle (MN) patch is proposed for long-term and effective treatment of AD by integrating therapeutic nanoparticles (NPs) and live bacteria. In the design, the MN tips are loaded with Prussian blue NPs encapsulating cetirizine hydrochloride (CET@PB NPs), while the patch backing incorporates Bacillus subtilis (B. subtilis). Upon skin insertion, the MN patch efficiently delivers CET@PB NPs into the skin and deposits live B. subtilis on the skin surface after fast dissolution. The delivered NPs not only scavenge reactive oxygen species (ROS) and improve oxidative stress microenvironments in the AD lesions, but also provide sustained release of the antihistamine CET in the skin for alleviating AD symptoms. Furthermore, B. subtilis survives on the skin for over 9 days and effectively inhibits the growth of the harmful bacteria Staphylococcus aureus. These features highlight the superior efficacy of the MN patch in long-term treatment of AD, offering a promising alternative for the management of skin disorders in clinics.

Atopic dermatitis treatment: A comprehensive review of conventional and novel bioengineered approaches

Atopic dermatitis (AD) remains a challenging condition, with conventional treatments often leading to adverse effects and limited efficacy. This review explores the diverse landscape of AD treatments, encompassing conventional methods, novel topical and systemic therapies, and emerging bioengineered strategies. While conventional drug administration often requires high dosages or frequent administration, leading to adverse effects, targeted biologics have shown promise. Phototherapy and wet wrap therapy, while helpful, have limitations. Given these factors, the need for modern and effective therapeutic strategies for AD is pressing. Complementary or alternative therapies have garnered significant attention in recent years as a compelling treatment for AD. Among these, functionalized biomaterials and textiles with physicochemical, nanotechnology-based characteristics, or bioengineered features are some of the most common typical adjuvant therapies. The multifunctional-engineered biomaterials, as a new generation of biomedical materials, and stem cells, seem to hold tremendous promise for the treatment of dermatological diseases like AD. Biomaterials have seen great success, especially in various medical fields, due to their unique and adaptable characteristics. These materials, including collagen, PCL, and PLGA, offer unique advantages, such as biocompatibility, biodegradability, controlled drug release, and enhanced drug retention.

Topographical variations in the skin barrier and their role in disease pathogenesis

The skin barrier can be divided into at least four functional units: chemical, microbial, physical and immunological barriers. The chemical and microbial barriers have previously been shown to exhibit different characteristics in topographically distinct skin regions. There is increasing evidence that the physical and immunological barriers also show marked variability in different areas of the skin. Here, we review recent data on the topographical variations of skin barrier components, the contribution of these variations to the homeostatic function of the skin and their impact on the pathogenesis of specific immune-mediated skin diseases (such as atopic dermatitis and papulopustular rosacea). Recognition of these topographical barrier differences will improve our understanding of skin homeostasis and disease pathogenesis and provide a basis for body site-specific targeted therapies.

Ferroptosis of select skin epithelial cells initiates and maintains chronic systemic immune-mediated psoriatic disease

Dysregulations of epithelial-immune interactions frequently culminate in chronic inflammatory diseases of the skin, lungs, kidneys, and gastrointestinal tract. Yet, the intraepithelial processes that initiate and perpetuate inflammation in these organs are poorly understood. Here, by utilizing redox lipidomics we identified ferroptosis-associated peroxidation of polyunsaturated phosphatidylethanolamines in the epithelia of patients with asthma, cystic fibrosis, psoriasis, and renal failure. Focusing on psoriasis as a disease model, we used high-resolution mass spectrometry imaging and identified keratin 14-expressing (K14-expressing) keratinocytes executing a ferroptotic death program in human psoriatic skin. Psoriatic phenotype with characteristic Th1/Th17 skin and extracutaneous immune responses was initiated and maintained in a murine model designed to actuate ferroptosis in a fraction of K14+ glutathione peroxidase 4-deficient (Gpx4-deficient) epidermal keratinocytes. Importantly, an antiferroptotic agent, liproxstatin-1, was as effective as clinically relevant biological IL-12/IL-23/TNF-α-targeting therapies or the depletion of T cells in completely abrogating molecular, biochemical, and morphological features of psoriasis. As ferroptosis in select epidermal keratinocytes triggers and sustains a pathological psoriatic multiorgan inflammatory circuit, we suggest that strategies targeting ferroptosis or its causes may be effective in preventing or ameliorating a variety of chronic inflammatory diseases.

Gut microbiota and skin pathologies: Mechanism of the gut-skin axis in atopic dermatitis and psoriasis

Atopic dermatitis (AD) and psoriasis are chronic skin diseases with a global impact, posing significant challenges to public health systems and severely affecting patients' quality of life. This review delves into the key role of the gut microbiota in these diseases, emphasizing the importance of the gut-skin axis in inflammatory mediators and immune regulation and revealing a complex bidirectional communication system. We comprehensively assessed the pathogenesis, clinical manifestations, and treatment strategies for AD and psoriasis, with a particular focus on how the gut microbiota and their metabolites influence disease progression via the gut-skin axis. In addition, personalized treatment plans based on individual patient microbiome characteristics have been proposed, offering new perspectives for future treatment approaches. We call for enhanced interdisciplinary cooperation to further explore the interactions between gut microbiota and skin diseases and to assess the potential of drugs and natural products in modulating the gut-skin axis, aiming to advance the treatment of skin diseases.

Systemic Implications of Bullous Pemphigoid: Bridging Dermatology and Internal Medicine

Background: Bullous pemphigoid is an autoimmune bullous disease that frequently affects a large skin surface area, but it can also present in localized areas. It has been hypothesized that bullous pemphigoid affects the systemic functioning of different organs because inflammatory cells and cytokines circulate throughout numerous organs. Results: Recent clinical and experimental studies have revealed an association between bullous pemphigoid and systemic organ disorders. To avoid the emergence of systemic organ diseases, the significance of systemic treatment in cases of severe bullous pemphigoid should be emphasized. Conclusions: Here, we discuss the specific molecular processes underlying typical systemic organ inflammatory diseases associated with bullous pemphigoids.

N6-methyladenosine modification-tuned lipid metabolism controls skin immune homeostasis via regulating neutrophil chemotaxis

Disrupted N6-methyladenosine (m6A) modification modulates various inflammatory disorders. However, the role of m6A in regulating cutaneous inflammation remains elusive. Here, we reveal that the m6A and its methyltransferase METTL3 are down-regulated in keratinocytes in inflammatory skin diseases. Inducible deletion of Mettl3 in murine keratinocytes results in spontaneous skin inflammation and increases susceptibility to cutaneous inflammation with activation of neutrophil recruitment. Therapeutically, restoration of m6A alleviates the disease phenotypes in mice and suppresses inflammation in human biopsy specimens. We support a model in which m6A modification stabilizes the mRNA of the lipid-metabolizing enzyme ELOVL6 via the m6A reader IGF2BP3, leading to a rewiring of fatty acid metabolism with a reduction in palmitic acid accumulation and, consequently, suppressing neutrophil chemotaxis in cutaneous inflammation. Our findings highlight a previously unrecognized epithelial-intrinsic m6A modification-lipid metabolism pathway that is essential for maintaining epidermal and immune homeostasis and lay the basis for potential therapeutic targeting of m6A modulators to attenuate inflammatory skin diseases.

Identification of novel hub genes and immune infiltration in atopic dermatitis using integrated bioinformatics analysis

The aim of this study was to identify key genes and investigate the immunological mechanisms of atopic dermatitis (AD) at the molecular level via bioinformatics analysis. Gene expression profiles (GSE32924, GSE107361, GSE121212, and GSE230200) were obtained for screening common differentially expressed genes (co-DEGs) from the gene expression omnibus database. Functional enrichment analysis, protein-protein interaction network and module construction, and identification of common hub genes were performed. Hub genes were validated using receiver operating characteristic curve analysis based on GSE130588 and GSE16161. NetworkAnalyst was used to detect microRNAs (miRNAs) and transcription factors (TFs) associated with the hub genes. The immune cell infiltration was analyzed using the CIBERSORT algorithm to further analyze the correlation between hub genes and immune cells. A total of 146 co-DEGs were obtained, showing significant enrichment in cytokine-cytokine receptor interaction and JAK-STAT signaling pathway. Seven hub genes were identified by Cytoscape and validated with external datasets. Subsequent prediction of miRNAs and TFs targeting these hub genes revealed their regulatory roles. Analysis of immune cell infiltration and correlation revealed a significant positive correlation between CCL22 expression and the number of dendritic cells activated. The identified hub genes represent potential diagnostic and therapeutic targets in the immunological pathogenesis of AD.

Diterpenoid DGT alleviates atopic dermatitis-like responses in vitro and in vivo via targeting IL-4Rα

BACKGROUND

Atopic dermatitis is a common chronic inflammatory skin disease characterized by relapsing eczema and intense itch. DGT is a novel synthetic heterocyclic diterpenoid derived from plants. Its therapeutic potential and mechanism(s) of action are poorly understood.

OBJECTIVES

We investigated the potent therapeutic effect of DGT on atopic dermatitis, exploring the underlying mechanisms and determining whether DGT is a safe and well-tolerated topical treatment.

METHODS

We observed anti-inflammatory effects of DGT on tumor necrosis factor-α/interferon-γ-treated human keratinocytes, and anti-allergic effects on immunoglobulin E-sensitized bone marrow-derived mast cells. In vivo, DGT was topically applied to two experimental mouse models of atopic dermatitis: oxazolone-induced sensitization and topically applied calcipotriol. Then the therapeutic effects of DGT were evaluated physiologically and morphologically. Moreover, we performed nonclinical toxicology and safety pharmacology research, including general toxicity, pharmacokinetics, and safety pharmacology on the cardiovascular, respiratory, and central nervous systems.

RESULTS

In keratinocytes, DGT reduced the expression of inflammatory factors, promoting the expression of barrier functional proteins and tight junctions and maintaining the steady state of barrier function. DGT also inhibited the activation and degranulation of mast cells induced by immunoglobulin E. Moreover, we found that interleukin-4 receptor-α was the possible target of DGT. Meanwhile, DGT had therapeutic effects on oxazolone/calcipotriol-treated mice. Notably, our pharmacology results demonstrated that DGT was safe and nontoxic in our studies.

CONCLUSION

DGT's potent anti-inflammatory effects and good safety profile suggest that it is a potential candidate for the treatment of atopic dermatitis.

Langerhans cells and skin immune diseases

Langerhans cells (LCs) are the key antigen-presenting cells in the epidermis in normal conditions and respond differentially to environmental and/or endogenous stimuli, exerting either proinflammatory or anti-inflammatory effects. Current knowledge about LCs mainly originates from studies utilizing mouse models, whereas with the development of single-cell techniques, there has been significant progress for human LCs, which has updated our understanding of the phenotype, ontogeny, differentiation regulation, and function of LCs. In this review, we delineated the progress of human LCs and summarized LCs' function in inflammatory skin diseases, providing new ideas for precise regulation of LC function in the prevention and treatment of skin diseases.

Intestinal permeability disturbances: causes, diseases and therapy

Nowadays, a pathological increase in the permeability of the intestinal barrier (the so-called leaky gut) is increasingly being diagnosed. This condition can be caused by various factors, mainly from the external environment. Damage to the intestinal barrier entails a number of adverse phenomena: dysbiosis, translocation of microorganisms deep into the intestinal tissue, immune response, development of chronic inflammation. These phenomena can ultimately lead to a vicious cycle that promotes the development of inflammation and further damage to the barrier. Activated immune cells in mucosal tissues with broken barriers can migrate to other organs and negatively affect their functioning. Damaged intestinal barrier can facilitate the development of local diseases such as irritable bowel disease, inflammatory bowel disease or celiac disease, but also the development of systemic inflammatory diseases such as rheumatoid arthritis, ankylosing spondylitis, hepatitis, and lupus erythematosus, neurodegenerative or psychiatric conditions, or metabolic diseases such as diabetes or obesity. However, it must be emphasized that the causal links between a leaky gut barrier and the onset of certain diseases often remain unclear and require in-depth research. In light of recent research, it becomes crucial to prevent damage to the intestinal barrier, as well as to develop therapies for the barrier when it is damaged. This paper presents the current state of knowledge on the causes, health consequences and attempts to treat excessive permeability of the intestinal barrier.

How underappreciated autoinflammatory (innate immunity) mechanisms dominate disparate autoimmune disorders

Historically inflammation against self was considered autoimmune which stems back to the seminal observations by Ehrlich who described serum factors, now known to be autoantibodies produced by B lineage cells that mediate "horror autotoxicus". The 20th century elucidation of B- and T-cell adaptive immune responses cemented the understanding of the key role of adaptive immune responses in mediating pathology against self. However, Mechnikov shared the Nobel Prize for the discovery of phagocytosis, the most rudimentary aspect of innate immunity. Fast forward some 100 years and an immunogenetic understanding of innate immunity led to the categorising of innate immunopathology under the umbrella term 'auto inflammation' and terminology such as "horror autoinflammaticus" to highlight the schism from the classical adaptive immune understanding of autoimmunity. These concepts lead to calls for a two-tiered classification of inflammation against self, but just as innate and adaptive immunity are functionally integrated, so is immunopathology in many settings and the concept of an autoimmune to autoinflammation continuum emerged with overlaps between both. Herein we describe several historically designated disorders of adaptive immunity where innate immunity is key, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), systemic juvenile idiopathic arthritis (sJIA) and adult-onset Still's disease (AOSD) where the immunopathology phenotype is strongly linked to major histocompatibility complex (MHC) class II associations and responds to drugs that target T-cells. We also consider MHC-I-opathies including psoriasis and Behcet's disease(BD) that are increasingly viewed as archetype CD8 T-cell related disorders. We also briefly review the key role of barrier dysfunction in eczema and ulcerative colitis (UC) where innate tissue permeability barrier dysfunction and microbial dysbiosis contributes to prominent adaptive immune pathological mechanisms. We also highlight the emerging roles of intermediate populations of lymphocytes including gamma delta (γδ) and mucosal-associated invariant T (MAIT) cells that represent a blend of adaptive immune plasticity and innate immune rapid responders that may also determine site specific patterns of inflammation.

The neuroscience of itch in relation to transdiagnostic psychological approaches

The experience of itch and its associated chronic conditions (i.e., atopic dermatitis) form a significant burden of disease. Knowledge of how the brain processes itch, that might occur uniquely for chronic itch populations, could be used to guide more effective psychotherapeutic interventions for these groups. To build the evidence base for such approaches, we conducted a series of coordinates-based fMRI analyses, to identify the shared neural mechanisms for itch across the published literature. Upon so doing, we identified a core "itch network" that spans the Basal Ganglia/Thalamus, Claustrum and Insula. Additionally, we found evidence that the Paracentral Lobule and Medial Frontal Gyrus, regions associated with cognitive control and response inhibition, deactivate during itch. Interestingly, a separate analysis for chronic itch populations identified significant recruitment of the Left Paracentral Lobule, potentially suggesting the recruitment of cognitive control mechanisms to resist the urge to scratch. We position these results in light of further integrative studies that could use neuroimaging alongside clinical studies, to explore how transdiagnostic psychological approaches-such as mindfulness and compassion training-might help to improve quality of life for individuals who experience chronic itch.

Insights from Traditional Chinese Medicine for Restoring Skin Barrier Functions

The skin barrier is essential for maintaining the body's internal homeostasis, protecting against harmful external substances, and regulating water and electrolyte balance. Traditional Chinese Medicine (TCM) offers notable advantages in restoring skin barrier function due to its diverse components, targets, and pathways. Recent studies have demonstrated that active ingredients in TCM can safely and effectively repair damaged skin barriers, reinstating their proper functions. This review article provides a comprehensive overview of the mechanisms underlying skin barrier damage and explores how the bioactive constituents of TCM contribute to skin barrier repair, thereby offering a theoretical framework to inform clinical practices.

Oncostatin M promotes epithelial barrier dysfunction in patients with eosinophilic chronic rhinosinusitis with nasal polyps

BACKGROUND

Oncostatin M (OSM) may be involved in the promotion of mucosal epithelial barrier dysfunction in patients with eosinophilic chronic rhinosinusitis with nasal polyps (Eos CRSwNP) by inducing matrix metalloproteinase (MMP) -1 and -7. The aim was to evaluate the roles and mechanisms of action of OSM on MMP-1 and -7 synthesis from nasal epithelial cells (NECs).

METHODS

OSM, OSM receptor (OSMR), MMP-1 and -7 expression was evaluated in nasal mucosa or primary NECs from scrapings by quantitative polymerase chain reaction (qPCR), immunofluorescence and immunohistochemistry. OSM and other cytokines were used to stimulate air-liquid interface (ALI) cultured NECs. qPCR, enzyme-linked immunosorbent assay (ELISA) and immunofluorescence were used to evaluate the expression of OSMR, MMP-1, -7 and occludin in NECs.

RESULTS

Elevated levels of OSMRβ, MMP-1 and -7 were found in the tissues and scraped NECs of Eos CRSwNP in comparison to them obtained from the inferior turbinate (IT) and control subjects. The levels of OSM and OSMRβ mRNA in tissues were positively correlated with the levels of MMP-1 and -7. OSM stimulation of NECs increased the expression of MMP-1 and -7, and the responses were suppressed by a STAT3 inhibitor, and a PI3K inhibitor respectively. In parallel studies, we found that stimulation with OSM disrupted the localization of occludin, a tight junction protein in NECs. The response was suppressed by a pan-MMP inhibitor.

CONCLUSION

OSM induces the synthesis and release of MMP-1 and -7 in NECs. Furthermore, MMP-1 and -7 promote mucosal epithelial barrier dysfunction in patients with Eos CRSwNP.

Pharmacologic inhibition of Il6st/gp130 improves dermatological inflammation and pruritus

Chronic dermatitis is a disease with large unmet need for pharmacological improvement. Dermatitis conditions are maintained and exacerbated by various cytokine actions in the context of inflammation. Interleukin 6 signal transducer (Il6st), also known as glycoprotein 130 (Gp130), is a key component for surface reception of a multitude of cytokines and transduction and amplification of their pro-inflammatory signals. We hypothesized accordingly that pharmacological inhibition of Il6st can alter dermatitis pathology. Treatment with SC-144 and bazedoxifene, two representative small molecule Il6st inhibitors with different binding modes led to moderate but significant improvement of skin conditions in a 1-chloro-2,4-dinitrobenzene animal model. Part of cytokine expressions indicating the dermatological index were normalized particularly when treated with SC-144. Pruritic behaviors were blunted, also possibly giving limited contribution to disease improvement. In psoriatic skin and itch of an imiquimod animal model, those two treatments appeared to be relatively moderate. Collectively, pharmacological inhibition of Il6st seems to lessen pathological irritation. Inversely, this experimental attempt newly implies that Il6st participates in pathological mechanisms. In conclusion, we suggest Il6st as a novel target for improving dermatitis, and that agents with suitable efficacy and safety for its modulation are translatable.

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.

p38α deficiency ameliorates psoriasis development by downregulating STAT3-mediated keratinocyte proliferation and cytokine production

Psoriasis is characterized by keratinocyte (KC) hyperproliferation and inflammatory cell infiltration, but the mechanisms remain unclear. In an imiquimod-induced mouse psoriasiform model, p38 activity is significantly elevated in KCs and p38α specific deletion in KCs ameliorates skin inflammation. p38α signaling promotes KC proliferation and psoriasis-related proinflammatory gene expression during psoriasis development. Mechanistically, p38α enhances KC proliferation and production of inflammatory cytokines and chemokines by activating STAT3. While p38α signaling in KCs does not affect the expression of IL-23 and IL-17, it substantially amplifies the IL-23/IL-17 pathogenic axis in psoriasis. The therapeutic effect of IL-17 neutralization is associated with decreased p38 and STAT3 activities in KCs and targeting the p38α-STAT3 axis in KCs ameliorates the severity of psoriasis. As IL-17 also highly activates p38 and STAT3 in KCs, our findings reveal a sustained signaling circuit important for psoriasis development, highlighting p38α-STAT3 axis as an important target for psoriasis treatment.

IL-17 family cytokines in inflammatory or autoimmune skin diseases

As potent pro-inflammatory mediators, IL-17 family cytokines play crucial roles in the pathogenesis of various inflammatory and autoimmune skin disorders. Although substantial progress has been achieved in understanding the pivotal role of IL-17A signaling in psoriasis, leading to the development of highly effective biologics, the functions of other IL-17 family members in inflammatory or autoimmune skin diseases remain less explored. In this review, we provide a comprehensive overview of IL-17 family cytokines and their receptors, with a particular focus on the recent advancements in identifying cellular sources, receptors and signaling pathways regulated by these cytokines. At the end, we discuss how the aberrant functions of IL-17 family cytokines contribute to the pathogenesis of diverse inflammatory or autoimmune skin diseases.

Exploring the Common Pathogenic Mechanisms of Psoriasis and Atopic Dermatitis: The Interaction between SGK1 and TIGIT Signaling Pathways

This study aims to explore the common pathogenic mechanisms of psoriasis and atopic dermatitis, two T-cell-mediated autoimmune diseases. Utilizing single-cell transcriptomic sequencing data, we revealed that Treg cells primarily express TIGIT in both psoriasis and atopic dermatitis, and identified a subset of macrophages that highly express SGK1. These cells can interact with T cells via the NECTIN2-TIGIT signaling pathway, inhibiting the differentiation of T cells into a pro-inflammatory phenotype, thereby uncovering a common immunoregulatory mechanism in both diseases. Furthermore, we discovered that inhibition of SGK1 exacerbates the inflammatory response in disease models of both conditions. These findings not only provide a new perspective for a common therapeutic strategy for psoriasis and atopic dermatitis but also highlight the importance of considering these molecular interactions in future treatments. Validation of these observations through further qPCR, immunofluorescence, and animal studies has identified potential new targets for the treatment of psoriasis and atopic dermatitis.

The interaction between NK cells and ILC cells and their subsets in atopic dermatitis patients with and without dupilumab therapy

BACKGROUND

Natural killer cells (NK) and innate lymphoid cells with their subsets (ILC) are part of the innate immune system.

OBJECTIVE

The aim is to evaluate how NK cells and ILC cells interact in atopic dermatitis (AD) patients (with and without dupilumab therapy) compared to control group.

MATERIALS AND METHODS

Complete dermatological examination was performed in all patients included in the study (19 AD patients with dupilumab, 17 AD patients without dupilumab). Surface molecules expressed on NK cells and ILC cells were analyzed by flow cytometry. The association between NK cells and total ILC cells, ILC-1, ILC-2, ILC-3, NCR+ILC3, NCR-ILC3 were compared in AD patients and in the control group. The non-parametric Spearman's rank correlation coefficient was used for this statistical analysis. We evaluated the association of parameters with AD severity at the time of treatment.Non-parametric Mann-Whitney, Kolmogorov-Smirnov tests were used.

RESULTS

We confirmed the higher association between NK cells and total ILC cells in AD patients without dupilumab therapy (in 30.3 %) and in healthy controls (in 27.2 %); this association is low in AD patients with dupilumab therapy (in 0.1 %). The higher association was confirmed between NK cells and ILCs subsets only in AD patients without dupilumab therapy; in these patients the highest association was confirmed between NK cells and ILC-2 cells (in 38.6 %). No statistically significant difference in the count of NK cells and ILC cells was found between mild and moderate form of AD patients treated with dupilumab.

CONCLUSION

Targeting these cell types or the cytokines they produce could represent potential therapeutic strategies for controlling inflammation and alleviating symptoms in AD patients.

Krill oil: nutraceutical potential in skin health and disease

Krill oil (KO), extracted from the Antarctic marine crustacean Euphausia superba, is a nutrient-dense substance that includes rich profiles of n-3 polyunsaturated fatty acids (n-3 PUFAs), phospholipids (PLs), astaxanthin (ASX), as well as vitamins A and E, minerals, and flavonoids. As a high-quality lipid resource, KO has been widely used as a dietary supplement for its health-protective properties in recent years. KO has various benefits, including antioxidative, anti-inflammatory, metabolic regulatory, neuroprotective, and gut microbiome modulatory effects. Especially, the antioxidant and anti-inflammatory effects make KO have potential in skin care applications. With increasing demands for natural skin anti-aging solutions, KO has emerged as a valuable nutraceutical in dermatology, showing potential for mitigating the effects of skin aging and enhancing overall skin health and vitality. This review provides an overview of existing studies on the beneficial impact of KO on the skin, exploring its functional roles and underlying mechanisms through which it contributes to dermatological health and disease management.

Depletion of Gsdma1/2/3 alleviates PMA-induced epidermal hyperplasia by inhibiting the EGFR-Stat3/Akt pathway

Homeostasis of the skin barrier is essential for maintaining normal skin function. Gasdermin A (GSDMA) is highly expressed in the skin and associated with many skin diseases, such as melanoma and psoriasis. In mice, GSDMA is encoded by three gene homologues, namely Gsdma1, Gsdma2, and Gsdma3. Although Gsdma3 gain-of-function mutations cause hair loss and skin inflammation, Gsdma3-deficient mice do not show any visible phenotypes in skin and hair structures. To explore the physiological function of GSDMA, we generated conventional Gsdma1/2/3 knockout (KO) mice. These mice showed significantly alleviated epidermal hyperplasia and inflammation induced by phorbol 12-myristate 13-acetate (PMA). Furthermore, the alleviation of epidermal hyperplasia depended on the expression of Gsdma1/2/3 specifically in keratinocytes. Mechanistically, Gsdma1/2/3 depletion downregulated epidermal growth factor receptor (EGFR) ligands, leading to the decreased EGFR-Stat3/Akt signalling. These results demonstrate that depletion of Gsdma1/2/3 alleviates PMA-induced epidermal hyperplasia partially by inhibiting the EGFR-Stat3/Akt pathway.

Single-cell technologies in psoriasis

Psoriasis is a chronic and recurrent inflammatory skin disorder. The primary manifestation of psoriasis arises from disturbances in the cutaneous immune microenvironment, but the specific functions of the cellular components within this microenvironment remain unknown. Recent advancements in single-cell technologies have enabled the detection of multi-omics at the level of individual cells, including single-cell transcriptome, proteome, and metabolome, which have been successfully applied in studying autoimmune diseases, and other pathologies. These techniques allow the identification of heterogeneous cell clusters and their varying contributions to disease development. Considering the immunological traits of psoriasis, an in-depth exploration of immune cells and their interactions with cutaneous parenchymal cells can markedly advance our comprehension of the mechanisms underlying the onset and recurrence of psoriasis. In this comprehensive review, we present an overview of recent applications of single-cell technologies in psoriasis, aiming to improve our understanding of the underlying mechanisms of this disorder.

Causal relationship between inflammatory skin diseases and breast cancer: A bidirectional Mendelian randomization study

INTRODUCTION

Prior research has explored the relationship between inflammatory skin disorders and breast cancer (BC), yet the causality of this association remains uncertain.

METHODS

Utilizing a bidirectional two-sample Mendelian randomization (MR) approach, this study aimed to elucidate the causal dynamics between various inflammatory skin conditions-namely acne, atopic dermatitis, psoriasis vulgaris, urticaria, and rosacea-and BC. Genetic variants implicated in these disorders were sourced from comprehensive genome-wide association studies representative of European ancestry. In the forward MR, BC was posited as the exposure, while the reverse MR treated each inflammatory skin disease as the exposure. A suite of analytical methodologies, including random effects inverse variance weighted (IVW), weighted median (WME), and MR-Egger, were employed to probe the causative links between inflammatory skin diseases and BC. Sensitivity analyses, alongside evaluations for heterogeneity and pleiotropy, were conducted to substantiate the findings.

RESULTS

The MR analysis revealed an increased risk of acne associated with BC (IVW: OR = 1.063, 95% CI = 1.011-1.117, p = 0.016), while noting a decreased risk of atopic dermatitis (AD) in BC patients (IVW: OR = 0.941, 95% CI = 0.886-0.999, p = 0.047). No significant associations were observed between BC and psoriasis vulgaris, urticaria, or rosacea. Conversely, reverse MR analyses detected no effect of BC on the incidence of inflammatory skin diseases. The absence of pleiotropy and the consistency of these outcomes strengthen the study's conclusions.

CONCLUSION

Findings indicate an elevated incidence of acne and a reduced incidence of AD in individuals with BC within the European population.

Sensory neurons increase keratinocyte proliferation through CGRP release in a tissue engineered in vitro model of innervation in psoriasis

Skin denervation has been shown to cause remission of psoriatic lesions in patients, which can reappear if reinnervation occurs. This effect can be induced by the activation of dendritic cells through sensory innervation. However, a direct effect of nerves on the proliferation of keratinocytes involved in the formation of psoriatic plaques has not been investigated. We developed, by tissue engineering, a model of psoriatic skin made of patient skin cells that showed increased keratinocyte proliferation and epidermal thickness compared to healthy controls. When this model was treated with CGRP, a neuropeptide released by sensory neurons, an increased keratinocyte proliferation was observed in the psoriatic skin model, but not in the control. When a sensory nerve network was incorporated in the psoriatic model and treated with capsaicin to induce neuropeptide release, an increase of keratinocyte proliferation was confirmed, which was blocked by a CGRP antagonist while no difference was noticed in the innervated healthy control. We showed that sensory neurons can participate directly to keratinocyte hyperproliferation in the formation of psoriatic lesions through the release of CGRP, independently of the immune system. Our unique tissue-engineered innervated psoriatic skin model could be a valuable tool to better understand the mechanism by which nerves may modulate psoriatic lesion formation in humans. STATEMENT OF SIGNIFICANCE: This study shows that keratinocytes extracted from patients' psoriatic skin retain, at least in part, the disease phenotype. Indeed, when combined in a 3D model of tissue-engineered psoriatic skin, keratinocytes exhibited a higher proliferation rate, and produced a thicker epidermis than a healthy skin control. In addition, their hyperproliferation was aggravated by a treatment with CGRP, a neuropeptide released by sensory nerves. In a innervated model of tissue-engineered psoriatic skin, an increase in keratinocyte hyperproliferation was also observed after inducing neurons to release neuropeptides. This effect was prevented by concomitant treatment with an antagonist to CGRP. Thus, this study shows that sensory nerves can directly participate to affect keratinocyte hyperproliferation in psoriasis through CGRP release.

Generalized Pustular Psoriasis and Systemic Organ Dysfunctions

This review explores the intricate relationship between generalized pustular psoriasis (GPP) and various systemic diseases, shedding light on the broader impacts of this severe skin condition beyond its primary dermatological manifestations. GPP is identified as not only a profound contributor to skin pathology but also a significant risk factor for systemic diseases affecting cardiovascular, hepatic, renal, pulmonary, and skeletal systems, as well as associated with an increased incidence of anemia, depression, anxiety, and arthritis. The research highlights the complex interplay of cytokines, particularly IL-17 and IL-36, which are central to the pathophysiology of GPP and implicated in the exacerbation of systemic conditions. Key findings indicate a higher incidence of cardiovascular events in GPP patients compared to those with other severe forms of psoriasis, notably with a stronger correlation between myocardial infarction history and GPP development. Liver disturbances, frequently reversible upon psoriasis remission, suggest a cytokine-mediated link to hepatic health. Renal dysfunction appears elevated in GPP sufferers, with IL-17 and IL-36 potentially driving renal fibrosis. Similarly, interstitial lung disease and osteoporosis in GPP patients underscore the systemic reach of inflammatory processes initiated in the skin. The associations with anemia, depression, anxiety, and arthritis further complicate the clinical management of GPP, requiring a multidisciplinary approach. The study concludes that managing GPP effectively requires a holistic approach that addresses both the cutaneous and systemic dimensions of the disease, advocating for continued research into the mechanisms that connect GPP with broader health implications to refine therapeutic strategies.

Epidermal barrier impairment predisposes for excessive growth of the allergy-associated yeast Malassezia on murine skin

BACKGROUND

The skin barrier is vital for protection against environmental threats including insults caused by skin-resident microbes. Dysregulation of this barrier is a hallmark of atopic dermatitis (AD) and ichthyosis, with variable consequences for host immune control of colonizing commensals and opportunistic pathogens. While Malassezia is the most abundant commensal fungus of the skin, little is known about the host control of this fungus in inflammatory skin diseases.

METHODS

In this experimental study, MC903-treated mice were colonized with Malassezia spp. to assess the host-fungal interactions in atopic dermatitis. Additional murine models of AD and ichthyosis, including tape stripping, K5-Nrf2 overexpression and flaky tail mice, were employed to confirm and expand the findings. Skin fungal counts were enumerated. High parameter flow cytometry was used to characterize the antifungal response in the AD-like skin. Structural and functional alterations in the skin barrier were determined by histology and transcriptomics of bulk skin. Finally, differential expression of metabolic genes in Malassezia in atopic and control skin was quantified.

RESULTS

Malassezia grows excessively in AD-like skin. Fungal overgrowth could, however, not be explained by the altered immune status of the atopic skin. Instead, we found that by upregulating key metabolic genes in the altered cutaneous niche, Malassezia acquired enhanced fitness to efficiently colonise the impaired skin barrier.

CONCLUSIONS

This study provides evidence that structural and metabolic changes in the dysfunctional epidermal barrier environment provide increased accessibility and an altered lipid profile, to which the lipid-dependent yeast adapts for enhanced nutrient assimilation. Our findings reveal fundamental insights into the implication of the mycobiota in the pathogenesis of common skin barrier disorders.

Atopic Dermatitis and Psoriasis: Similarities and Differences in Metabolism and Microbiome

Atopic dermatitis and psoriasis are common chronic inflammatory diseases of high incidence that share some clinical features, including symptoms of pruritus and pain, scaly lesions, and histologically, acanthosis and hyperkeratosis. Meanwhile, they are both commonly comorbid with metabolic disorders such as obesity and diabetes, indicating that both diseases may exist with significant metabolic disturbances. Metabolomics reveals that both atopic dermatitis and psoriasis have abnormalities in a variety of metabolites, including lipids, amino acids, and glucose. Meanwhile, recent studies have highlighted the importance of the microbiome and its metabolites in the pathogenesis of atopic dermatitis and psoriasis. Metabolic alterations and microbiome dysbiosis can also affect the immune, inflammatory, and epidermal barrier, thereby influencing the development of atopic dermatitis and psoriasis. Focusing on the metabolic and microbiome levels, this review is devoted to elaborating the similarities and differences between atopic dermatitis and psoriasis, thus providing insights into the intricate relationship between both conditions.

TRPV3-Activated PARP1/AIFM1/MIF Axis through Oxidative Stress Contributes to Atopic Dermatitis

TRPV3 is a temperature-sensitive calcium-permeable channel. In previous studies, we noticed prominent TUNEL-positive keratinocytes in patients with Olmsted syndrome and Trpv3+/G568V mice, both of which carry gain-of-function variants in the TRPV3 gene. However, it remains unclear how the keratinocytes die and whether this process contributes to more skin disorders. In this study, we showed that gain-of-function variant or pharmacological activation of TRPV3 resulted in poly(ADP-ribose) polymerase 1 (PARP1)/AIFM1/macrophage migration inhibitory factor axis-mediated parthanatos, which is an underestimated form of cell death in skin diseases. Chelating calcium, scavenging ROS, or inhibiting nitric oxide synthase effectively rescued the parthanatos, indicating that TRPV3 regulates parthanatos through calcium-mediated oxidative stress. Furthermore, inhibiting PARP1 downregulated TSLP and IL33 induced by TRPV3 activation in HaCaT cells, reduced immune cell infiltration, and ameliorated epidermal thickening in Trpv3+/G568V mice. Marked parthanatos was also detected in the skin of MC903-treated mice and patients with atopic dermatitis, whereas inhibiting PARP1 largely alleviated the MC903-induced dermatitis. In addition, stimulating parthanatos in mouse skin with methylnitronitrosoguanidine recapitulated many features of atopic dermatitis. These data demonstrate that the TRPV3-regulated parthanatos-associated PARP1/AIFM1/macrophage migration inhibitory factor axis is a critical contributor to the pathogenesis of Olmsted syndrome and atopic dermatitis, suggesting that modulating the PARP1/AIFM1/macrophage migration inhibitory factor axis is a promising therapy for these conditions.

Role of Ubiquitin-conjugating enzyme E2 (UBE2) in two immune-mediated inflammatory skin diseases: a mendelian randomization analysis

Psoriasis vulgaris (PV) and Atopic dermatitis (AD) are the two major types of immune-mediated inflammatory skin disease (IMISD). Limited studies reported the association between Ubiquitin-conjugating enzyme E2 (UBE2) and IMISD. We employed a two-sample Mendelian randomization (MR) study to assess the causality between UBE2 and PV & AD. UBE2 association genome-wide association study (GWAS) data were collected. The inverse variance weighted (IVW) method was utilized as the principal method in our Mendelian randomization (MR) study, with additional using the MR-Egger, weighted median, simple mode, and weighted mode methods. The MR-Egger intercept test, Cochran's Q test, MR-Pleiotropy RESidual Sum and Outlier (MR-PRESSO) and leave-one-out analysis were conducted to identify heterogeneity and pleiotropy, colocalization analysis was also performed. The results showed that Ubiquitin-conjugating enzyme E2 variant 1 (UBE2V1) was causally associated with PV (OR = 0.909, 95% CI: 0.830-0.996, P = 0.040), Ubiquitin-conjugating enzyme E2 L3 (UBE2L3) was causally associated with AD (OR = 0.799, 95% CI: 0.709-0.990, P < 0.001). Both UBE2V1 and UBE2L3 may play protective roles in patients with PV or AD, respectively. No other significant result has been investigated. No heterogeneity or pleiotropy was observed. This study provided new evidence of the relationship between UBE2V1 and PV, UBE2L3 and AD. Our MR suggested that UBE2V1 plays an inhibitory role in PV progression, UBE2L3 plays an inhibitory role in AD. These could be novel and effective ways to treat PV and AD.

Screening mitochondria-related biomarkers in skin and plasma of atopic dermatitis patients by bioinformatics analysis and machine learning

Background

There is a significant imbalance of mitochondrial activity and oxidative stress (OS) status in patients with atopic dermatitis (AD). This study aims to screen skin and peripheral mitochondria-related biomarkers, providing insights into the underlying mechanisms of mitochondrial dysfunction in AD.

Methods

Public data were obtained from MitoCarta 3.0 and GEO database. We screened mitochondria-related differentially expressed genes (MitoDEGs) using R language and then performed GO and KEGG pathway analysis on MitoDEGs. PPI and machine learning algorithms were also used to select hub MitoDEGs. Meanwhile, the expression of hub MitoDEGs in clinical samples were verified. Using ROC curve analysis, the diagnostic performance of risk model constructed from these hub MitoDEGs was evaluated in the training and validation sets. Further computer-aided algorithm analyses included gene set enrichment analysis (GSEA), immune infiltration and mitochondrial metabolism, centered on these hub MitoDEGs. We also used real-time PCR and Spearman method to evaluate the relationship between plasma circulating cell-free mitochondrial DNA (ccf-mtDNA) levels and disease severity in AD patients.

Results

MitoDEGs in AD were significantly enriched in pathways involved in mitochondrial respiration, mitochondrial metabolism, and mitochondrial membrane transport. Four hub genes (BAX, IDH3A, MRPS6, and GPT2) were selected to take part in the creation of a novel mitochondrial-based risk model for AD prediction. The risk score demonstrated excellent diagnostic performance in both the training cohort (AUC = 1.000) and the validation cohort (AUC = 0.810). Four hub MitoDEGs were also clearly associated with the innate immune cells' infiltration and the molecular modifications of mitochondrial hypermetabolism in AD. We further discovered that AD patients had considerably greater plasma ccf-mtDNA levels than controls (U = 92.0, p< 0.001). Besides, there was a significant relationship between the up-regulation of plasma mtDNA and the severity of AD symptoms.

Conclusions

The study highlights BAX, IDH3A, MRPS6 and GPT2 as crucial MitoDEGs and demonstrates their efficiency in identifying AD. Moderate to severe AD is associated with increased markers of mitochondrial damage and cellular stress (ccf=mtDNA). Our study provides data support for the variation in mitochondria-related functional characteristics of AD patients.

Sprayable Zwitterionic Antibacterial Hydrogel With High Mechanical Resilience and Robust Adhesion for Joint Wound Treatment

Wound healing in movable parts, including the joints and neck, remains a critical challenge due to frequent motions and poor flexibility of dressings, which may lead to mismatching of mechanical properties and poor fitting between dressings and wounds; thus, increasing the risk of bacterial infection. This study proposes a sprayable zwitterionic antibacterial hydrogel with outstanding flexibility and desirable adhesion. This hydrogel precursor is fabricated by combining zwitterionic sulfobetaine methacrylate (SBMA) with poly(sulfobetaine methacrylate-co-dopamine methacrylamide)-modified silver nanoparticles (PSBDA@AgNPs) through robust electrostatic interactions. About 150 s of exposure to UV light, the SBMA monomer polymerizes to form PSB chains entangled with PSBDA@AgNPs, transformed into a stable and adhesion PSB-PSB@Ag hydrogel at the wound site. The resulting hydrogel has adhesive strength (15-38 kPa), large tensile strain (>400%), suitable shape adaptation, and excellent mechanical resilience. Moreover, the hydrogel displays pH-responsive behavior; the acidic microenvironment at the infected wound sites prompts the hydrogel to rapidly release AgNPs and kill bacteria. Further, the healing effect of the hydrogel is demonstrated on the rat neck skin wound, showing improved wound closing rate due to reduced inflammation and enhanced angiogenesis. Overall, the sprayable zwitterionic antibacterial hydrogel has significant potential to promote joint skin wound healing.

Molecular and cellular pruritus mechanisms in the host skin

Pruritus, also known as itching, is a complex sensation that involves the activation of specific physiological and cellular receptors. The skin is innervated with sensory nerves as well as some receptors for various sensations, and its immune system has prominent neurological connections. Sensory neurons have a considerable impact on the sensation of itching. However, immune cells also play a role in this process, as they release pruritogens. Disruption of the dermal barrier activates an immune response, initiating a series of chemical, physical, and cellular reactions. These reactions involve various cell types, including keratinocytes, as well as immune cells involved in innate and adaptive immunity. Collective activation of these immune responses confers protection against potential pathogens. Thus, understanding the molecular and cellular mechanisms that contribute to pruritus in host skin is crucial for the advancement of effective treatment approaches. This review provides a comprehensive analysis of the present knowledge concerning the molecular and cellular mechanisms underlying itching signaling in the skin. Additionally, this review explored the integration of these mechanisms with the broader context of itch mediators and the expression of their receptors in the skin.

Nanotechnology strategies to address challenges in topical and cellular delivery of siRNAs in skin disease therapy

Gene therapy is one of the most advanced therapies in current medicine. In particular, interference RNA-based therapy by small interfering RNA (siRNA) has gained attention in recent years as it is a highly versatile, selective and specific therapy. In dermatological conditions, topical delivery of siRNA offers numerous therapeutic advantages, mainly by inhibiting the expression of target transcripts directly in the skin. However, crossing the stratum corneum and overcoming intracellular barriers is an inherent challenge. Substantial efforts by scientists have moved towards the use of multimodal and multifunctional nanoparticles to overcome these barriers and achieve greater bioavailability in their site of action, the cytoplasm. In this review the most innovative strategies based on nanoparticle and physical methods are presented, as well as the design principles and the main factors that contribute to the performance of these systems. This review also highlights the synergistic contributions of medicine, nanotechnology, and molecular biology to advancing translational research into siRNA-based therapeutics for skin diseases.

Skin barrier-inflammatory pathway is a driver of the psoriasis-atopic dermatitis transition

As chronic inflammatory conditions driven by immune dysregulation are influenced by genetics and environment factors, psoriasis and atopic dermatitis (AD) have traditionally been considered to be distinct diseases characterized by different T cell responses. Psoriasis, associated with type 17 helper T (Th17)-mediated inflammation, presents as well-defined scaly plaques with minimal pruritus. AD, primarily linked to Th2-mediated inflammation, presents with poorly defined erythema, dry skin, and intense itching. However, psoriasis and AD may overlap or transition into one another spontaneously, independent of biological agent usage. Emerging evidence suggests that defects in skin barrier-related molecules interact with the polarization of T cells, which forms a skin barrier-inflammatory loop with them. This loop contributes to the chronicity of the primary disease or the transition between psoriasis and AD. This review aimed to elucidate the mechanisms underlying skin barrier defects in driving the overlap between psoriasis and AD. In this review, the importance of repairing the skin barrier was underscored, and the significance of tailoring biologic treatments based on individual immune status instead of solely adhering to the treatment guidelines for AD or psoriasis was emphasized.

A Staphylococcus epidermidis strain inhibits the uptake of Staphylococcus aureus derived from atopic dermatitis skin into the keratinocytes

BACKGROUND

Various bacterial species form a microbiome in the skin. In the past, dead Staphylococcus aureus derived from atopic dermatitis (AD) are taken up by keratinocytes; however, whether live S. aureus can be taken up by keratinocytes is unknown.

OBJECTIVE

This study aimed to examine whether live AD strains of S. aureus internalize into the keratinocytes and how the internalization changes under conditions in which other bacterial species including S. epidermidis are present.

METHODS

HaCaT cells were cultured with live S. aureus and S. epidermidis (live or heat-treated) or their culture supernatants. After coculture, the change in the amount of S. aureus in the cytoplasm of HaCaT cells was analyzed using, a high-throughput imaging system, Opera Phenix™.

RESULTS

Live S. aureus were taken up in the cytoplasm of HaCaT cells. Coculturing live S. aureus with live S. epidermidis or the culture supernatants decreased the abundance of S. aureus in the cytoplasm. The heat-treated culture supernatants of live S. epidermidis or culture supernatants of other S. strains did not decrease the abundance of S. aureus in the cytoplasm.

CONCLUSION

Live S. aureus was internalized into the cytoplasm of HaCaT cells as does heat-treated S. aureus. In addition, the heat-sensitive substances secreted by coculture with S. epidermidis and keratinocytes inhibited the uptake of S. aureus by keratinocytes.

Cell Type-Specific Extracellular Vesicles and Their Impact on Health and Disease

Extracellular vesicles (EVs), a diverse group of cell-derived exocytosed particles, are pivotal in mediating intercellular communication due to their ability to selectively transfer biomolecules to specific cell types. EVs, composed of proteins, nucleic acids, and lipids, are taken up by cells to affect a variety of signaling cascades. Research in the field has primarily focused on stem cell-derived EVs, with a particular focus on mesenchymal stem cells, for their potential therapeutic benefits. Recently, tissue-specific EVs or cell type-specific extracellular vesicles (CTS-EVs), have garnered attention for their unique biogenesis and molecular composition because they enable highly targeted cell-specific communication. Various studies have outlined the roles that CTS-EVs play in the signaling for physiological function and the maintenance of homeostasis, including immune modulation, tissue regeneration, and organ development. These properties are also exploited for disease propagation, such as in cancer, neurological disorders, infectious diseases, autoimmune conditions, and more. The insights gained from analyzing CTS-EVs in different biological roles not only enhance our understanding of intercellular signaling and disease pathogenesis but also open new avenues for innovative diagnostic biomarkers and therapeutic targets for a wide spectrum of medical conditions. This review comprehensively outlines the current understanding of CTS-EV origins, function within normal physiology, and implications in diseased states.

Therapeutic potential of adipose derived stromal cells for major skin inflammatory diseases

Inflammatory skin diseases like psoriasis and atopic dermatitis are chronic inflammatory skin conditions continuously under investigation due to increased prevalence and lack of cure. Moreover, long-term treatments available are often associated with adverse effects and drug resistance. Consequently, there is a clear unmet need for new therapeutic approaches. One promising and cutting-edge treatment option is the use of adipose-derived mesenchymal stromal cells (AD-MSCs) due to its immunomodulatory and anti-inflammatory properties. Therefore, this mini review aims to highlight why adipose-derived mesenchymal stromal cells are a potential new treatment for these diseases by summarizing the pre-clinical and clinical studies investigated up to date and addressing current limitations and unresolved clinical questions from a dermatological and immunomodulatory point of view.

Single-cell transcriptome analysis reveals keratinocyte subpopulations contributing to psoriasis in corneum and granular layer

BACKGROUND

Psoriasis is a chronic, inflammatory skin disease that is common and relapses easily. While the importance of keratinocyte proliferation in psoriasis development is well-documented, the specific functional subpopulations of epidermal keratinocytes associated with this disease remain enigmatic.

MATERIALS AND METHODS

Therefore, in our analysis of single-cell transcriptome data from both normal and psoriatic skin tissues, we observed significant increases in certain keratinocytes in the stratum corneum (KC) and stratum granulosum (KG) within psoriatic skin. Furthermore, we identified upregulated expression of specific secreted factors known to promote inflammatory responses. Additionally, we conducted a KEGG pathway enrichment analysis on these identified subsets.

RESULTS

In the stratum corneum, the expression of FTL was upregulated in HIST1H1C+ KC. S100P+ KC displayed a significant increase in the expression of both S100P and S100A10, whereas PRR9+ KC showed upregulated expression of DEFB4B, S100A8, and S100A12. SLURP1+ KC was characterized by elevated expression levels of IL-36G, SLURP1, and S100A12. Meanwhile, in the stratum granulosum, KRT1+ KG highly expressed SLURP1, S100A7, S100A8, and S100A9, while DEFB4B expression was upregulated in PI3+ KG. Our findings indicated that subsets within the stratum corneum primarily participate in pathways related to MAPK, NOD-like receptors, HIF-1, cell senescence, and other crucial processes. In contrast, subsets in the stratum granulosum were predominantly associated with pathways involving MAPK, NOD-like receptors, HIF-1, Hippo, mTOR, and IL-17.

CONCLUSION

These findings not only uncover the keratinocyte subsets linked to psoriasis but also unveil the molecular mechanisms and related signaling pathways that drive psoriasis development. This knowledge opens new horizons for the development of innovative clinical treatment strategies for psoriasis.