Current insights into the role of human β-defensins in atopic dermatitis

AMP-IBP5: A Multifunctional Antimicrobial Peptide for Advanced Wound Healing and Inflammatory Skin Disorders

Wound healing is a complex, multiphase process crucial for restoring tissue integrity and functionality after injury. Among the emerging therapeutic approaches, antimicrobial peptides (AMPs) have shown substantial promise because of their dual role in microbial defense and cellular modulation. AMP-IBP5, a novel AMP derived from insulin-like growth factor-binding protein 5, exhibits both antimicrobial and wound-healing properties, making it a promising therapeutic candidate. This peptide exhibits robust antimicrobial activity, augments keratinocyte proliferation, increases fibroblast migration, induces angiogenesis, and modulates the immune response. Mechanistically, AMP-IBP5 activates Mas-related G protein-coupled receptors and low-density lipoprotein receptor-related protein 1 (LRP1) in keratinocytes, stimulating IL-8 production and vascular endothelial growth factor expression to accelerate wound healing. This molecule also interacts with LRP1 in fibroblasts to increase cell migration and promote angiogenesis while mitigating inflammatory responses through targeted cytokine modulation. Preclinical studies have demonstrated its remarkable efficacy in promoting tissue repair in diabetic wounds and inflammatory skin conditions, including atopic dermatitis and psoriasis. This review delves into the broad therapeutic potential of AMP-IBP5 across dermatological applications, focusing on its intricate mechanisms of action, comparative advantages, and its path toward clinical and commercial application.

Antimicrobial peptides and their application to combat implant-associated infections - opportunities and challenges

Despite minimally invasive surgeries and advancements in aseptic techniques, implant-associated infections are a significant complication in post-surgical implantation of medical devices. The standard practice of systemic antibiotic administration is often ineffective due to the development of bacterial antibiotic resistance, poor antibiotic penetration into biofilms, and low antibiotic bioavailability at the infected site. Infected implants are typically salvaged by tissue resection and antibacterial reinforcements during revision surgery. Towards this end, antimicrobial peptides (AMPs) have emerged as a promising alternative to traditional antibiotics to combat infections. Herein, a comprehensive overview of antimicrobial peptides, their structure and function, comparison with conventional antibiotics, antimicrobial properties, mechanisms of action of AMPs, and bacterial resistance to AMPs in relation to antibiotics are discussed. Furthermore, stimuli-responsive AMP delivery and contact killing via AMP coatings on implant surfaces are deliberated. We discuss various methods of AMP immobilization and coatings on implant materials through physico-chemical coating strategies. The review also addresses the clinical status and current limitations of AMP coatings such as proteolytic instability and potential cytotoxicity. Finally, we conclude with future directions to develop small, effective AMP mimetics and encapsulation of AMPs within nanocarriers to improve antimicrobial properties and design-controlled release systems for sustained antimicrobial activity.

Beyond the classic players: Mas-related G protein-coupled receptor member X2 role in pruritus and skin diseases

Chronic spontaneous urticaria (CSU), atopic dermatitis (AD), psoriasis and rosacea are highly prevalent inflammatory skin conditions which impose a significant burden on patients' quality of life. Their pathophysiology is likely multifactorial, involving genetic, immune and environmental factors. Recent advancements in the field have demonstrated the key role of mast cells (MC) in the pathophysiology of these conditions. The Mas-related G protein-coupled receptor X2 (MRGPRX2) has emerged as a promising non-IgE-mediated MC activation receptor. MRGPRX2 is predominately expressed on MC and activated by endogenous and exogenous ligands, leading to MC degranulation and release of various pro-inflammatory mediators. Mounting evidence on the presence of endogenous MRGPRX2 agonists (substance P, cortistatin-14, LL37, PAMP-12 and VIP) and its high expression among patients with CSU, AD, rosacea, psoriasis and chronic pruritus emphasizes the pathogenic role of MRGPRX2 in these conditions. Despite the currently available treatments, there remains a pressing need for novel drug targets and treatment options for these chronic inflammatory skin conditions. Here, we reviewed the pathogenic role of MRGPRX2 and its potential as a novel therapeutic target and provided an update on future research directions.

Correlation and Clinical Significance of HBD-2 and CXCL-1/2 Levels at Skin Lesions with Psoriasis Vulgaris Severity

OBJECTIVE

This study was performed to explore the clinical significance of the expression of human beta-defensin 2 (HBD-2) and chemokine ligand 1/2 (CXCL-1/2) in psoriasis vulgaris.

METHODS

This study retrospectively included the study group (n = 160) and control group (n = 100) for analysis. The levels of inflammatory indicators, blood biochemical indicators, and immune indicators using ELISA. The psoriasis area and severity index (PASI) was used to evaluate disease severity. Levels of HBD-2, CXCL-1, CXCL-2 and CCL20 were determined by RT-PCR. The correlations of HBD-2, CXCL-1 and CXCL-2 levels with CCL20 and PASI scores were analyzed. The diagnostic value of HBD-2, CXCL-1 and CXCL-2 in psoriasis vulgaris was analyzed by ROC curve.

RESULTS

HBD-2, CXCL-1 and CXCL-2 were highly expressed in the lesions of psoriasis vulgaris patients, and were positively correlated with CCL20 and PASI score. HBD-2, CXCL-1 and CXCL-2 alone or in combination had high diagnostic value for psoriasis vulgaris and severe psoriasis, and the combined diagnostic value of the three was higher than that of a single indicator.

CONCLUSION

HBD-2, CXCL-1, and CXCL-2 levels are closely related to the severity of psoriasis vulgaris and can effectively diagnose the occurrence and progression of psoriasis vulgaris.

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.

Human β-defensins: The multi-functional natural peptide

The increasing threat of antibiotic resistance among pathogenic microorganisms and the urgent demand for new antibiotics require immediate attention. Antimicrobial peptides exhibit effectiveness against microorganisms, fungi, viruses, and protozoa. The discovery of human β-defensins represents a major milestone in biomedical research, opening new avenues for scientific investigation into the innate immune system and its resistance mechanisms against pathogenic microorganisms. Multiple defensins present a promising alternative in the context of antibiotic abuse. However, obstacles to the practical application of defensins as anti-infective therapies persist due to the unique properties of human β-defensins themselves and serious pharmacological and technical challenges. To overcome these challenges, diverse delivery vehicles have been developed and progressively improved for the conjugation or encapsulation of human β-defensins. This review briefly introduces the biology of human β-defensins, focusing on their multistage structure and diverse functions. It also discusses several heterologous systems for producing human β-defensins, various delivery systems created for these peptides, and patent applications related to their utilization, concluding with a summary of current challenges and potential solutions.

Human Beta Defensin-2 mRNA and Proteasome Subunit β Type 8 mRNA Analysis, Useful in Differentiating Skin Biopsies from Atopic Dermatitis and Psoriasis Vulgaris Patients

(1): Atopic dermatitis and psoriasis vulgaris are chronic, inflammatory diseases. Clinical presentation usually leads to a proper diagnosis, but sometimes neither clinical examination nor histopathological evaluation can be conclusive. Therefore, we aimed to build up a novel diagnostic tool and check it for accuracy. The main objective of our work was to differentiate between healthy skin (C), atopic dermatitis (AD) and psoriasis vulgaris (PV) biopsies on the base of involucrin (IVL) and human β-defensin-2 (hBD-2) concentrations and their mRNA, as well as mRNA for TPP2 and PSMB8. (2): ELISA for IVL and hBD-2 proteins and Real-time PCR for the relative expression of mRNA for: IVL (IVL mRNA), hBD-2 (hBD-2 mRNA), PSMB8 (PSMB8 mRNA) and TPP2 (TPP2 mRNA), isolated from skin biopsies taken from AD and PV patients and healthy volunteers were performed. (3): hBD-2 mRNA and PSMB8 mRNA correlated with some parameters of clinical assessment of inflammatory disease severity. hBD-2 mRNA expression, exclusively, was sufficient to distinguish inflammatory skin biopsies from the healthy ones. (4): hBD-2 mRNA and PSMB8 mRNA analysis were the most valuable parameters in differentiating AD and PV biopsies.

Impact of Skin Exposure to Benzo[a]pyrene in Rat Model: Insights into Epidermal Cell Function and Draining Lymph Node Cell Response

The skin is a direct target of the air pollutant benzo[a]pyrene (BaP). While its carcinogenic qualities are well-studied, the immunotoxicity of BaP after dermal exposure is less understood. This study examines the immunomodulatory effects of a 10-day epicutaneous BaP application, in environmentally/occupationally relevant doses, by analyzing ex vivo skin immune response (skin explant, epidermal cells and draining lymph node/DLN cell activity), alongside the skin's reaction to sensitization with experimental hapten dinitrochlorobenzene (DNCB). The results show that BaP application disrupts the structure of the epidermal layer and promotes immune cell infiltration in the dermis. BaP exposure led to oxidative stress in epidermal cells, characterized by decreased reduced glutathione and increased AHR and Cyp1A1 expression. Production and gene expression of proinflammatory cytokines (TNF, IL-1β) by epidermal cells decreased, while IL-10 response increased. Decreased spontaneous production of IFN-γ and IL-17, along with unchanged IL-10, was observed in DLC cells, whereas ConA-stimulated production of these cytokines was elevated. Local immunosuppression caused by BaP application seems to reduce the skin's response to an additional stimulus, evidenced by decreased effector activity of DLN cells three days after sensitization with DNCB. These findings provide new insight into the immunomodulatory effects and health risks associated with skin exposure to BaP.

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.

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.

Filaggrin and beyond: New insights into the skin barrier in atopic dermatitis and allergic diseases, from genetics to therapeutic perspectives

Atopic dermatitis (AD) is the most common inflammatory skin disease worldwide, affecting 20% of children and 5% of adults. One critical component in the pathophysiology of AD is the epidermal skin barrier, with its outermost layer, the stratum corneum (SC), conferring biochemical properties that enable resilience against environmental threats and maintain homeostasis. The skin barrier may be conceptualized as a key facilitator of complex interactions between genetics, host immunity, the cutaneous microbiome, and environmental exposures. The key genetic risk factor for AD development and persistence is a loss-of-function mutation in FLG, with recent advances in genomics focusing on rare variant discovery, establishment of pathogenic mechanisms, and exploration of the role of other epidermal differentiation complex gene variants in AD. Aberrant type 2 inflammatory responses down-regulate the transcription of key epidermal barrier genes, alter the composition of SC lipids, and induce further injury through a neurocutaneous feedback loop and the itch-scratch cycle. The dysbiotic epidermis exhibits reduced bacterial diversity and enhanced colonization with Staphylococcus and Malassezia species, which contribute to both direct barrier injury through the action of bacterial toxins and perpetuation of the inflammatory cascades. Enhanced understanding of each of the pathogenic mechanisms underpinning barrier disruption has led to the development of novel topical and systemic molecules, including interleukin (IL)-4Ra, IL-13, PDE4, and Janus-associated kinase inhibitors, whose clinical effectiveness exceeds conventional treatment modalities. In this narrative review, we aim to summarize the current understanding of the above-mentioned pathophysiological and therapeutic mechanisms, with a focus on the genetic, cellular, and molecular mechanisms underpinning AD development.

Non-Invasive Assessment of Skin Surface Proteins of Psoriasis Vulgaris Patients in Response to Biological Therapy

Measurements of skin surface biomarkers have enormous value for the detailed assessment of skin conditions, both for clinical application and in skin care. The main goals of the current study were to assess whether expression patterns of skin surface hBD-1, hBD-2, IL-1α, CXCL-1, and CXCL-8, examples of proteins known to be involved in psoriasis pathology, are associated with disease severity and whether expression patterns of these proteins on the skin surface can be used to measure pharmacodynamic effects of biological therapy. In this observational study using transdermal analysis patch (TAP), levels of skin surface IL-1α, hBD-1, hBD-2, CXCL-1/2, and CXCL-8 of psoriasis vulgaris (PV) patients over biological therapy were assessed. The Psoriasis Area Severity Index (PASI) and local score for erythema, induration, and desquamation were determined from the exact same skin area as FibroTx TAP measurements. Thirty-seven adult PV patients were included, of which twenty-three were subjected to anti-TNF-α, seven to anti-IL-17A, and seven to anti-IL12/IL-23 therapy. Significantly higher levels of hBD-1, hBD-2, CXCL-1/2, and CXCL-8 were detected on lesional skin compared to the non-lesional skin of the PV patients. In contrast, lower levels of IL-1α were found in lesional skin compared to non-lesional skin. In addition, we observed that the biomarker expression levels correlate with disease severity. Further, we confirmed that changes in the expression levels of skin surface biomarkers during biological therapy correlate with treatment response. Biomarker expression patterns in response to treatment differed somewhat between treatment subtypes. We observed that, in the case of anti-TNF-α therapy, an increase after a steady decrease in the expression levels of CXCL-1/2 and CXCL-8 occurred before the change in clinical scores. Moreover, response kinetics of skin surface proteins differs between the applied therapies-hBD2 expression responds quickly to anti-IL-17A therapy, CXCL-1/2 to anti-IL-12/23, and levels of CXCL-8 are rapidly down-regulated by IL-17A and IL-12/23 therapy. Our findings confirm that the skin surface hBD-2, IL-1α, CXCL-1/2, and CXCL-8 are markers for the psoriasis severity. Further, data obtained during this study give the basis for the conclusion that skin surface proteins CXCL-1/2 and CXCL-8 may have value as therapeutic biomarkers, thus confirming that measuring the 'molecular root' of inflammation appears to have value in scoring disease severity on its own.

Staphylococcus aureus Adaptation to the Skin in Health and Persistent/Recurrent Infections

Staphylococcus aureus is a microorganism with an incredible capability to adapt to different niches within the human body. Approximately between 20 and 30% of the population is permanently but asymptomatically colonized with S. aureus in the nose, and another 30% may carry S. aureus intermittently. It has been established that nasal colonization is a risk factor for infection in other body sites, including mild to severe skin and soft tissue infections. The skin has distinct features that make it a hostile niche for many bacteria, therefore acting as a strong barrier against invading microorganisms. Healthy skin is desiccated; it has a low pH at the surface; the upper layer is constantly shed to remove attached bacteria; and several host antimicrobial peptides are produced. However, S. aureus is able to overcome these defenses and colonize this microenvironment. Moreover, this bacterium can very efficiently adapt to the stressors present in the skin under pathological conditions, as it occurs in patients with atopic dermatitis or suffering chronic wounds associated with diabetes. The focus of this manuscript is to revise the current knowledge concerning how S. aureus adapts to such diverse skin conditions causing persistent and recurrent infections.

Skin surface biomarkers are associated with future development of atopic dermatitis in children with family history of allergic disease

BACKGROUND

Atopic dermatitis (AD) is a common childhood chronic inflammatory skin disorder that can significantly impact quality of life and has been linked to the subsequent development of food allergy, asthma, and allergic rhinitis, an association known as the "atopic march."

OBJECTIVE

The aim of this study was to identify biomarkers collected non-invasively from the skin surface in order to predict AD before diagnosis across a broad age range of children.

METHODS

Non-invasive skin surface measures and biomarkers were collected from 160 children (3-48 months of age) of three groups: (A) healthy with no family history of allergic disease, (B) healthy with family history of allergic disease, and (C) diagnosed AD.

RESULTS

Eleven of 101 children in group B reported AD diagnosis in the subsequent 12 months following the measurements. The children who developed AD had increased skin immune markers before disease onset, compared to those who did not develop AD in the same group and to the control group. In those enrolled with AD, lesional skin was characterized by increased concentrations of certain immune markers and transepidermal water loss, and decreased skin surface hydration.

CONCLUSIONS

Defining risk susceptibility before onset of AD through non-invasive methods may help identify children who may benefit from early preventative interventions.

Mechanisms and regulation of defensins in host defense

As a family of cationic host defense peptides, defensins are mainly synthesized by Paneth cells, neutrophils, and epithelial cells, contributing to host defense. Their biological functions in innate immunity, as well as their structure and activity relationships, along with their mechanisms of action and therapeutic potential, have been of great interest in recent years. To highlight the key research into the role of defensins in human and animal health, we first describe their research history, structural features, evolution, and antimicrobial mechanisms. Next, we cover the role of defensins in immune homeostasis, chemotaxis, mucosal barrier function, gut microbiota regulation, intestinal development and regulation of cell death. Further, we discuss their clinical relevance and therapeutic potential in various diseases, including infectious disease, inflammatory bowel disease, diabetes and obesity, chronic inflammatory lung disease, periodontitis and cancer. Finally, we summarize the current knowledge regarding the nutrient-dependent regulation of defensins, including fatty acids, amino acids, microelements, plant extracts, and probiotics, while considering the clinical application of such regulation. Together, the review summarizes the various biological functions, mechanism of actions and potential clinical significance of defensins, along with the challenges in developing defensins-based therapy, thus providing crucial insights into their biology and potential clinical utility.

Apigenin: A Therapeutic Agent for Treatment of Skin Inflammatory Diseases and Cancer

The skin is the main barrier between the body and the environment, protecting it from external oxidative stress induced by ultraviolet rays. It also prevents the entrance of infectious agents such as viruses, external antigens, allergens, and bacteria into our bodies. An overreaction to these agents causes severe skin diseases, including atopic dermatitis, pruritus, psoriasis, skin cancer, and vitiligo. Members of the flavonoid family include apigenin, quercetin, luteolin, and kaempferol. Of these, apigenin has been used as a dietary supplement due to its various biological activities and has been shown to reduce skin inflammation by downregulating various inflammatory markers and molecular targets. In this review, we deal with current knowledge about inflammatory reactions in the skin and the molecular mechanisms by which apigenin reduces skin inflammation.

Genetic/Environmental Contributions and Immune Dysregulation in Children with Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common skin conditions in humans. AD affects up to 20% of children worldwide and results in morbidity for both patients and their caregivers. The basis of AD is an interplay between genetics and the environment characterized by immune dysregulation. A myriad of mutations that compromise the skin barrier and/or immune function have been linked to AD. Of these, filaggrin gene (FLG) mutations are the most evidenced. Many other mutations have been implicated in isolated studies that are often unreplicated, creating an archive of genes with potential but unconfirmed relevance to AD. Harnessing big data, polygenic risk scores (PRSs) and genome-wide association studies (GWAS) may provide a more practical strategy for identifying the genetic signatures of AD. Epigenetics may also play a role. Staphylococcus aureus is the most evidenced microbial contributor to AD. Cutaneous dysbiosis may result in over-colonization by pathogenic strains and aberrant skin immunity and inflammation. Aeroallergens, air pollution, and climate are other key environmental contributors to AD. The right climate and/or commensals may improve AD for some patients.

Human-β-defensin-3 attenuates atopic dermatitis-like inflammation through autophagy activation and the aryl hydrocarbon receptor signaling pathway

Human β-defensin-3 (hBD-3) exhibits antimicrobial and immunomodulatory activities; however, its contribution to autophagy regulation remains unclear, and the role of autophagy in the regulation of the epidermal barrier in atopic dermatitis (AD) is poorly understood. Here, keratinocyte autophagy was restrained in the skin lesions of patients with AD and murine models of AD. Interestingly, hBD-3 alleviated the IL-4– and IL-13–mediated impairment of the tight junction (TJ) barrier through keratinocyte autophagy activation, which involved aryl hydrocarbon receptor (AhR) signaling. While autophagy deficiency impaired the epidermal barrier and exacerbated inflammation, hBD-3 attenuated skin inflammation and enhanced the TJ barrier in AD. Importantly, hBD-3–mediated improvement of the TJ barrier was abolished in autophagy-deficient AD mice and in AhR-suppressed AD mice, suggesting a role for hBD-3–mediated autophagy in the regulation of the epidermal barrier and inflammation in AD. Thus, autophagy contributes to the pathogenesis of AD, and hBD-3 could be used for therapeutic purposes.

Multiple Roles for Cytokines in Atopic Dermatitis: From Pathogenic Mediators to Endotype-Specific Biomarkers to Therapeutic Targets

Atopic dermatitis (AD) is one of the most common chronic inflammatory skin diseases, which generally presents with intense itching and recurrent eczematous lesions. AD affects up to 20% of children and 10% of adults in high-income countries. The prevalence and incidence of AD have increased in recent years. The onset of AD mostly occurs in childhood, although in some cases AD may persist in adult life or even manifest in middle age (adult-onset AD). AD pathophysiology is made of a complex net, in which genetic background, skin barrier dysfunction, innate and adaptive immune responses, as well as itch contribute to disease development, progression, and chronicization. One of the most important features of AD is skin dehydration, which is mainly caused by filaggrin mutations that determine trans-epidermal water loss, pH alterations, and antigen penetration. In accordance with the “outside-inside” theory of AD pathogenesis, in a context of an altered epidermal barrier, antigens encounter epidermal antigen presentation cells (APCs), such as epidermal Langerhans cells and inflammatory epidermal dendritic cells, leading to their maturation and Th-2 cell-mediated inflammation. APCs also bear trimeric high-affinity receptors for immunoglobulin E (IgE), which induce IgE-mediated sensitizations as part of pathogenic mechanisms leading to AD. In this review, we discuss the role of cytokines in the pathogenesis of AD, considering patients with various clinical AD phenotypes. Moreover, we describe the cytokine patterns in patients with AD at different phases of the disease evolution, as well as in relation to different phenotypes/endotypes, including age, race, and intrinsic/extrinsic subtypes. We also discuss the outcomes of current biologics for AD, which corroborate the presence of multiple cytokine axes involved in the background of AD. A deep insight into the correlation between cytokine patterns and the related clinical forms of AD is a crucial step towards increasingly personalized, and therefore more efficient therapy.

House dust mite sensitization and exposure affects bronchial epithelial anti-microbial response to viral stimuli in patients with asthma

Introduction

Allergen exposure worsens viral‐triggered asthma exacerbations and could predispose the host to secondary bacterial infections. We have previously demonstrated that exposure to house dust mite (HDM) reduced TLR‐3‐induced IFN‐β in human bronchial epithelial cells (HBECs) from healthy donors. We hypothesize that HDM sensitization in different ways may be involved in both viral and bacterial resistance of HBECs in asthma. In this study, the role of HDM sensitization and effects of HDM exposure on viral stimulus‐challenged HBECs from asthmatic donors have been explored with regard to expression and release of molecules involved in anti‐viral and anti‐bacterial responses, respectively.

Methods

HBECs from HDM‐sensitized (HDM+) and unsensitized (HDM‐) patients with asthma were used. HBECs were exposed to HDM or heat inactivated (hi)‐HDM (20 μg/ml) for 24 h prior to stimulation with the viral infection mimic, Poly(I:C), for 3 or 24 h. Samples were analyzed with ELISA and RT‐qPCR for β‐defensin‐2, IFN‐β, TSLP, and neutrophil‐recruiting mediators: IL‐8 and TNF‐⍺. NFκB signaling proteins p105, p65, and IκB‐⍺ were analyzed by Western blot.

Results

Poly(I:C)‐induced IFN‐β expression was reduced in HBECs from HDM + compared to HDM‐ patients (p = 0.05). In vitro exposure of HBECs to HDM furthermore reduced anti‐microbial responses to Poly(I:C) including β‐defensin‐2, IL‐8, and TNF‐⍺, along with reduced NFκB activity. This was observed in HBECs from asthma patients sensitized to HDM, as well as in non‐sensitized patients. By contrast, Poly (I:C)‐induced release of TSLP, a driver of T2 inflammation, was not reduced with exposure to HDM.

Conclusion

Using HBECs challenged with viral infection mimic, Poly(I:C), we demonstrated that allergic sensitization to HDM was associated with impaired anti‐viral immunity and that HDM exposure reduced anti‐viral and anti‐bacterial defense molecules, but not TSLP, across non‐allergic as well as allergic asthma. These data suggest a role of HDM in the pathogenesis of asthma exacerbations evoked by viral infections including sequential viral‐bacterial and viral‐viral infections.

Human β-Defensin 2 and Its Postulated Role in Modulation of the Immune Response

Studies described so far suggest that human β-defensin 2 is an important protein of innate immune response which provides protection for the human organism against invading pathogens of bacterial, viral, fungal, as well as parasitical origin. Its pivotal role in enhancing immunity was proved in infants. It may also be considered a marker of inflammation. Its therapeutic administration has been suggested for maintenance of the balance of systemic homeostasis based on the appropriate composition of the microbiota. It has been suggested that it may be an important therapeutic tool for modulating the response of the immune system in many inflammatory diseases, offering new treatment modalities. For this reason, its properties and role in the human body discussed in this review should be studied in more detail.

A review of the mechanisms of keratinocytes damage caused by Staphylococcus aureus infection in patients with atopic dermatitis

The dysregulation of skin microflora in patients with atopic dermatitis (AD) has become a research hotspot in recent years. Metagenomic studies have shown that microbial diversity is decreased, whereas the Staphylococcus aureus infection is increased in AD. Keratinocytes are the primary barrier against the invasion of external pathogenic microorganisms. Staphylococcus aureus infection can abnormally activate innate and adaptive immune responses in keratinocytes, resulting in a vicious cycle between Staphylococcus aureus infection and AD. This article reviews the mechanisms of inflammatory damage of keratinocytes induced by Staphylococcus aureus infection in patients with AD, providing a theoretical basis for the study of new targeted drugs. This review also suggests for the management of Staphylococcus aureus infection in patients with AD.

Role of antimicrobial peptides in atopic dermatitis

Host defense peptides (HDPs) or antimicrobial peptides (AMPs) are short cationic amphipathic peptides of divergent sequences, which are part of the innate immune system and produced by various types of cells and tissues. The predominant role of HDPs is to respond to and protect humans against infection and inflammation. Common human HDPs include defensins, cathelicidin, psoriasin, dermcidin, and ribonucleases, but these peptides may be dysregulated in the skin of patients with atopic dermatitis (AD). Current evidence suggests that the antimicrobial properties and immunomodulatory effects of HDPs are involved in AD pathogenesis, making HDPs research a promising area for predicting disease severity and developing novel treatments for AD. In this review, we describe a potential role for human HDPs in the development, exacerbation, and progression of AD and propose their potential therapeutic benefits.

Keratinocytes: innate immune cells in atopic dermatitis

The skin is a unique immune organ that constitutes a complex network of physical, chemical and microbiological barriers against external insults. Keratinocytes are the most abundant cell type in the epidermis. These cells form the physical skin barrier and represent the first line of the host defense system by sensing pathogens via innate immune receptors, initiating anti-microbial responses and producing various cytokines, chemokines and anti-microbial peptides, which are important events in immunity. A damaged epidermal barrier in atopic dermatitis allows the penetration of potential allergens and pathogens to activate keratinocytes. Among the dysregulation of immune responses in atopic dermatitis, activated keratinocytes play a role in several biological processes that contribute to the pathogenesis of atopic dermatitis. In this review, we summarize the current understanding of the innate immune functions of keratinocytes in the pathogenesis of atopic dermatitis, with a special emphasis on skin-derived anti-microbial peptides and atopic dermatitis-related cytokines and chemokines in keratinocytes. An improved understanding of the innate immunity mediated by keratinocytes can provide helpful insight into the pathophysiological processes of atopic dermatitis and support new therapeutic efforts.

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

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

Mas-related G protein-coupled receptor X2 and its activators in dermatologic allergies

The Mas-related G protein-coupled receptor X2 (MRGPRX2) is a multiligand receptor responding to various exogenous and endogenous stimuli. Being highly expressed on skin mast cells, MRGPRX2 triggers their degranulation and release of proinflammatory mediators, and it promotes multicellular signaling cascades, such as itch induction and transmission in sensory neurons. The expression of MRGPRX2 by skin mast cells and the levels of the MRGPRX2 agonists (eg, substance P, major basic protein, eosinophil peroxidase) are upregulated in the serum and/or skin of patients with inflammatory and pruritic skin diseases, such as chronic spontaneous urticaria or atopic dermatitis. Therefore, MRGPRX2 and its agonists might be potential biomarkers for the progression of cutaneous inflammatory diseases and the response to treatment. In addition, they may represent promising targets for prevention and treatment of signs and symptoms in patients with skin diseases or drug reactions. To assess this possibility, this review explores the role and relevance of MRGPRX2 and its activators in cutaneous inflammatory disorders and chronic pruritus.

Potential role of the skin microbiota in Inflammatory skin diseases

BACKGROUND

Inflammatory skin diseases include a variety of skin diseases, such as seborrheic dermatitis, acne, atopic dermatitis, psoriasis and so on, which are more common and tend to have a significant impact on patients' quality of life. Inflammatory skin diseases often result in physical or psychological distress; however, the pathogenesis of these diseases have not been clearly elucidated. Many factors are involved in the pathogenesis of inflammatory skin diseases, including heredity, environment, immunity, epidermal barrier, mental disorders, infection and so on. In recent years, skin microbiota has been shown to play an important role in inflammatory skin diseases.

AIMS

To elaborate on the specific mechanisms of inflammatory skin diseases induced by microbiota dysbiosis.

METHODS

We introduce the function and influence of skin microbiota in inflammatory skin diseases from the following aspects: Immunity, epigenetics, epidermal barrier and treatment.

RESULTS

Skin microbiota can affect many aspects of the host, such as Immunity, epigenetics, epidermal barrier, and it plays an important role in the pathogenesis of inflammatory skin diseases.

CONCLUSION

Skin microbiota is extremely important for maintaining the health of skin and the dysbiosis of skin microbiota is an important pathogenesis of inflammatory skin diseases.

The Dichotomous Responses Driven by β-Defensins

Defensins are short, rapidly evolving, cationic antimicrobial host defence peptides with a repertoire of functions, still incompletely realised, that extends beyond direct microbial killing. They are released or secreted at epithelial surfaces, and in some cases, from immune cells in response to infection and inflammation. Defensins have been described as endogenous alarmins, alerting the body to danger and responding to inflammatory signals by promoting both local innate and adaptive systemic immune responses. However, there is now increasing evidence that they exert variable control on the response to danger; creating a dichotomous response that can suppress inflammation in some circumstances but exacerbate the response to danger and damage in others and, at higher levels, lead to a cytotoxic effect. Focussing in this review on human β-defensins, we discuss the evidence for their functions as proinflammatory, immune activators amplifying the response to infection or damage signals and/or as mediators of resolution of damage, contributing to a return to homeostasis. Finally, we consider their involvement in the development of autoimmune diseases.

Molecular Profiling of Keratinocyte Skin Tumors Links Staphylococcus aureus Overabundance and Increased Human β-Defensin-2 Expression to Growth Promotion of Squamous Cell Carcinoma

The skin microbiota plays a prominent role in health and disease; however, its contribution to skin tumorigenesis is not well understood. We comparatively assessed the microbial community compositions from excision specimens of the main human non-melanoma skin cancers, actinic keratosis (AK), squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). Keratinocyte skin tumors are characterized by significantly different microbial community compositions, wherein AK and SCC are more similar to each other than to BCC. Notably, in SCC, which represents the advanced tumor entity and frequently develops from AK, overabundance of Staphylococcus aureus, a known skin pathogen, was noted. Moreover, S. aureus overabundance was significantly associated with increased human β-defensin-2 (hBD-2) expression in SCC. By challenging human SCC cell lines with S. aureus, a specific induction of hBD-2 expression and increased tumor cell growth was seen. Increased proliferation was also induced by directly challenging SCC cells with hBD-2. Together, our data indicate that a changed microbial community composition in SCC, specified by S. aureus overabundance, might promote tumor cell growth via modulation of hBD-2 expression.

Sodium butyrate suppresses NOD1-mediated inflammatory molecules expressed in bovine hepatocytes during iE-DAP and LPS treatment

Nucleotide oligomerization domain protein-1 (NOD1), a cytosolic pattern recognition receptor for the γ-D-glutamyl-meso-diaminopimelic acid (iE-DAP) is associated with the inflammatory diseases. Very little is known how bovine hepatocytes respond to specific ligands of NOD1 and sodium butyrate (SB). Therefore, the aim of our study was to investigate the role of bovine hepatocytes in NOD1-mediated inflammation during iE-DAP or LPS treatment or SB pretreatment. To achieve this aim, hepatocytes separated from cows at ∼160 days in milk (DIM) were divided into six groups: The nontreated control group (CON), the iE-DAP-treated group (DAP), the lipopolysaccharide-treated group (LPS), iE-DAP with SB group (DSB), LPS with SB group (LSB), and the SB group. Both iE-DAP and LPS highly increased the expression of both NOD1 and RIPK2, the two key factors for the immune response in hepatocytes. IκBα, NF-κB/p65, and MAP kinases (ERK, JNK, and p38) were activated through phosphorylation. The activation of NF-κB and MAPK pathway consequently increased the proinflammatory cytokines, IL-6, TNF-α, IL-8, and IFN-γ and the chemokines CCL5, CCL20, and CXCL-10. Both treatments improved iNOS/NOS2 expression. However, iE-DAP was failed to express acute phase protein SAA3, but HP and LPS HP but SAA3. These ligands also increased LRRK2, TAK1, TAB1, and β-defensins expression. The SB pretreatment at lower dose restored the function of hepatocytes by suppressing these increased molecules, as HDAC3 was inhibited. The activated NOD1 negatively regulated the expression of FOXA2. Altogether these data suggest an important role of bovine hepatocytes to promote immune responses via NOD1 expression during infection in the liver and a key role of SB to attenuate inflammation.

Cat Allergy as a Source Intensification of Atopic Dermatitis in Adult Patients

Atopic dermatitis (AD) is characterized by exacerbations and remissions of eczematous skin, underlain by impaired skin barrier and aberrant Th2-type and Th-22 cytokine production. A number of allergens, in particular contact with fur animals, may aggravate the disease. This study seeks to define the influence of having a regular contact with a pet cat at home on the severity of symptoms and signs of AD. We addressed the issue using the SCORing Atopic Dermatitis (SCORAD) and visual analog (VAS) scores to assess the intensity of pruritus and by measuring the blood content of specific IgE and IL-4, IL-13, and IL-22 cytokines. The study group consisted of 47 adult patients suffering from AD since childhood, 18 of whom declared having regular contact with a cat and the remaining 29 who denied it. There also was a control group consisted of 16 healthy volunteers with no AD signs. The SCORAD and VAS scores were significantly higher in patients in contact with a cat than in those without it (median SCORAD 61.0 vs. 50.4 and VAS 9.0 vs. 4.0 points, respectively). The sIgE of a majority of patients (94.4%) in contact with a cat was in Class V-VI, compared with just a few patients (3.4%) with no such contact, having sIgE in the same classes (p < 0.001). Significant correlations were revealed between SCORAD and VAS scores and the class level of serum sIgE value. In addition, IL-22 was a single elevated cytokine, only in the patients in contact with a cat, and it correlated with pruritus severity. The results of the study underline the need to beware of the cat fur allergen, and they stress forethought and caution in acquiring and keeping a pet cat by patients suffering from AD.

Loss-of-function mutations in caspase recruitment domain-containing protein 14 (CARD14) are associated with a severe variant of atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a highly prevalent chronic inflammatory skin disease that is known to be, at least in part, genetically determined. Mutations in caspase recruitment domain-containing protein 14 (CARD14) have been shown to result in various forms of psoriasis and related disorders.

OBJECTIVE

We aimed to identify rare DNA variants conferring a significant risk for AD through genetic and functional studies in a cohort of patients affected with severe AD.

METHODS

Whole-exome and direct gene sequencing, immunohistochemistry, real-time PCR, ELISA, and functional assays in human keratinocytes were used.

RESULTS

In a cohort of patients referred with severe AD, DNA sequencing revealed in 4 patients 2 rare heterozygous missense mutations in the gene encoding CARD14, a major regulator of nuclear factor κB (NF-κB). A dual luciferase reporter assay demonstrated that both mutations exert a dominant loss-of-function effect and result in decreased NF-κB signaling. Accordingly, immunohistochemistry staining showed decreased expression of CARD14 in patients' skin, as well as decreased levels of activated p65, a surrogate marker for NF-κB activity. CARD14-deficient or mutant-expressing keratinocytes displayed abnormal secretion of key mediators of innate immunity.

CONCLUSIONS

Although dominant gain-of-function mutations in CARD14 are associated with psoriasis and related diseases, loss-of-function mutations in the same gene are associated with a severe variant of AD.

Influence of gender on epithelial host defence peptide gene expression under non-infected and infected conditions: A basic medical research study

Bacterial resistance against conventional antibiotics is increasing. This introduces challenges, for example, in the treatment of infected surgical wounds. Host defence peptides (HDP), which are endogenous peptide antibiotics, show broad-spectrum antimicrobial effectiveness. They protect the organism against pathological microorganisms. Synthetic HDP might supplement or even become alternatives to conventional antibiotics. Knowledge of their quantities under physiological and pathophysiological conditions is therefore required. The influence of gender on HDP expression is unknown. This study evaluates whether gender influences HDP expression in infected or healthy epithelium. Expression levels of HDP human beta-defensin (hBD)-1, -2 and -3 and psoriasin (S100A7) were analysed, by using real-time polymerase chain reaction, in samples of epithelium from infected surgical wounds (n = 20) and healthy epithelium (n = 14) from the neck in a basic medical research study (analytic observational design). The results demonstrated a significantly elevated expression of hBD-2, hBD-3 and psoriasin (P = 0.001 each) in infected epithelium compared with healthy epithelium. No difference in HDP expression levels was evident between samples from female and male patients, either within infected samples or within healthy epithelium samples. Thus, gender does not affect the cutaneous expression of the investigated HDP. This is fundamental knowledge for the study and potential use of HDP derivates as alternative antibiotic substances.

From cholesterol to consciousness

The nature of consciousness has been debated for centuries. It can be understood as part and parcel of the natural progression of life from unicellular to multicellular, calcium fluxes mediating communication within and between cells. Consciousness is the vertical integration of calcium fluxes, mediated by the Target of Rapamycin gene integrated with the cytoskeleton. The premise of this paper is that there is a fundamental physiologic integration of the organism with the environment that constitutes consciousness.