Expression of antimicrobial peptides in atopic dermatitis and possible immunoregulatory functions

TH2-driven manifestations of inborn errors of immunity

Monogenic lesions in pathways critical for effector functions responsible for immune surveillance, protection against autoinflammation, and appropriate responses to allergens and microorganisms underlie the pathophysiology of inborn errors of immunity (IEI). Variants in cytokine production, cytokine signaling, epithelial barrier function, antigen presentation, receptor signaling, and cellular processes and metabolism can drive autoimmunity, immunodeficiency, and/or allergic inflammation. Identification of these variants has improved our understanding of the role that many of these proteins play in skewing toward TH2-related allergic inflammation. Early-onset or atypical atopic disease, often in conjunction with immunodeficiency and/or autoimmunity, should raise suspicion for an IEI. This becomes a diagnostic dilemma if the initial clinical presentation is solely allergic inflammation, especially when the prevalence of allergic diseases is becoming more common. Genetic sequencing is necessary for IEI diagnosis and is helpful for early recognition and implementation of targeted treatment, if available. Although genetic evaluation is not feasible for all patients with atopy, identifying atopic patients with molecular immune abnormalities may be helpful for diagnostic, therapeutic, and prognostic purposes. In this review, we focus on IEI associated with TH2-driven allergic manifestations and classify them on the basis of the affected molecular pathways and predominant clinical manifestations.

Characterization of Different Inflammatory Skin Conditions in a Mouse Model of DNCB-Induced Atopic Dermatitis

The mouse model of 2,4-dinitrochlorbenzene (DNCB)-induced human-like atopic dermatitis (hlAD) has been widely used to test novel treatment strategies and compounds. However, the study designs and methods are highly diverse, presenting different hlAD disease patterns that occur after sensitization and repeated challenge with DNCB on dorsal skin. In addition, there is a lack of information about the progression of the disease during the experiment and the achieved pheno- and endotypes, especially at the timepoint when therapeutic treatment is initiated. We here examine hlAD in a DNCB-induced BALB/cJRj model at different timepoints: (i) before starting treatment with dexamethasone, representing a standard drug control (day 12) and (ii) at the end of the experiment (day 22). Both timepoints display typical AD-associated characteristics: skin thickening, spongiosis, hyper- and parakeratosis, altered cytokine and gene expression, increased lipid mediator formation, barrier protein and antimicrobial peptide abnormalities, as well as lymphoid organ hypertrophy. Increased mast cell infiltration into the skin and elevated immunoglobulin E plasma concentrations indicate a type I allergy response. The DNCB-treated skin showed an extrinsic moderate sub-acute hlAD lesion at day 12 and an extrinsic mild sub-acute to chronic pheno- and endotype at day 22 with a dominating Th2 response. A dependency of the filaggrin formation and expression in correlation to the disease severity in the DNCB-treated skin was found. In conclusion, our study reveals a detailed classification of a hlAD at two timepoints with different inflammatory skin conditions and pheno- and endotypes, thereby providing a better understanding of the DNCB-induced hlAD model in BALB/cJRj mice.

The pivotal role of Bifida Ferment Lysate on reinforcing the skin barrier function and maintaining homeostasis of skin defenses in vitro

BACKGROUND

The semiactive or inactive probiotics or their extracts used in dermatology have interesting properties to ameliorate signs of irritated skin and enhance the skin barrier. Bifidobacterium, as the most common probiotics, which has been found to be effective in reducing acne and improving the skin barrier function of atopic dermatitis. Bifida Ferment Lysate (BFL) can be obtained from Bifidobacterium by fermentation and extraction.

PURPOSE

In this study, we investigated the effect of a topically used BFL on the skin using in vitro evaluation methods.

RESULTS

The results showed that upregulation of skin physical barrier gene (FLG, LOR, IVL, TGM1, and AQP3) and antimicrobial peptide gene (CAMP and hBD-2) in HaCaT cells by BFL might be responsible for skin barrier resistance. In addition, BFL had strong antioxidant properties representing a dose-dependent increasing of the scavenging capacity of DPPH, ABTS, hydroxyl, and superoxide radicals. BFL treatment also fundamentally inhibited the intracellular ROS and MDA production and improved the activities of antioxidant enzymes (CAT and GSH-Px) in H2 O2 -stimulated HaCaT cells. As a good immunomodulatory factor, BFL efficiently decreased the secretion of IL-8 and TNF-α cytokines, and COX-2 mRNA expression in LPS-induced THP-1 macrophages.

CONCLUSION

BFL can strengthen the skin barrier function and stimulate skin barrier resistance, to reinforce the skin against oxidative stress and inflammatory stimuli.

Th1 regulatory events by infectious pathogens, herpes zoster and herpes simplex viruses: prospects for therapeutic options for atopic eczema

Infections caused by viral and bacterial pathogens are typically perceived as harmful, such as in cases of herpes zoster and herpes simplex virus infections. However, clinical observation of an improvement in atopic skin lesions upon herpes virus infection has been noted, particularly at the site of varicella and Kaposi’s varicelliform eruption. Th1 immune cells and cytokines, mobilized and induced for protection against infectious pathogens, are expected to improve Th2 dominant atopic symptoms. This study focuses on Th1 immunoregulatory events mediated by infectious pathogens, particularly herpes viruses. Immunoregulatory events induced by herpes viruses may have a potential therapeutic value for treating atopic eczema.

Liposomes encapsulating novel antimicrobial peptide Omiganan: Characterization and its pharmacodynamic evaluation in atopic dermatitis and psoriasis mice model

Omiganan is a novel 12 amino acid synthetic cationic peptide from the cathelicidin family. Omiganan possesses antimicrobial action against a wide range of microbes, including gram-positive and gram-negative bacteria and fungi. Omiganan mainly acts by depolarizing the cytoplasmic membrane, resulting in cellular disruption and death. Apart from its antimicrobial effect, Omiganan also has anti-inflammatory activity. The present investigation aimed to evaluate and compare the efficacy of Omiganan liposomal gel with conventional formulations (Omiganan gel and lotion) in atopic dermatitis (AD) and psoriasis mice animal models. Liposomes encapsulating Omiganan were prepared using the reverse-phase evaporation technique and incorporated into Carbopol 934P gel. The optimized Omiganan liposomes were then characterized for various physicochemical parameters such as vesicle size, shape and surface morphology, zeta-potential, rheological parameters, in-vitro drug release, ex-vivo skin permeation/deposition, in-vitro antimicrobial activity, proteolytic stability, and cellular toxicity and uptake studies. Liposomes exhibited 72 % encapsulation with 7.8 % loading efficacy, a vesicle size, and zeta potential of 120 nm and - 17.2 mv, respectively. Moreover, Omiganan liposomal gel demonstrated controlled release and a better permeation profile than conventional formulations. A substantial reduction in levels of pro-inflammatory cytokines and improvement in AD and psoriatic lesions were achieved by Omiganan liposomal gel compared to Omiganan gel and lotion-based formulations. The present study confirms that Omiganan liposomal formulation can be an effective, safe, and novel alternative treatment approach in atopic dermatitis and psoriasis.

Staphylococcus aureus Activates the Aryl Hydrocarbon Receptor in Human Keratinocytes

Staphylococcus aureus is an important pathogen causing various infections, including - as most frequently isolated bacterium - cutaneous infections. Keratinocytes as the first barrier cells of the skin respond to S. aureus by the release of defense molecules such as cytokines and antimicrobial peptides. Although several pattern recognition receptors expressed in keratinocytes such as Toll-like and NOD-like receptors have been reported to detect the presence of S. aureus, the mechanisms underlying the interplay between S. aureus and keratinocytes are still emerging. Here, we report that S. aureus induced gene expression of CYP1A1 and CYP1B1, responsive genes of the aryl hydrocarbon receptor (AhR). AhR activation by S. aureus was further confirmed by AhR gene reporter assays. AhR activation was mediated by factor(s) <2 kDa secreted by S. aureus. Whole transcriptome analyses and real-time PCR analyses identified IL-24, IL-6, and IL-1beta as cytokines induced in an AhR-dependent manner in S. aureus-treated keratinocytes. AhR inhibition in a 3D organotypic skin equivalent confirmed the crucial role of the AhR in mediating the induction of IL-24, IL-6, and IL-1beta upon stimulation with living S. aureus. Taken together, we further highlight the important role of the AhR in cutaneous innate defense and identified the AhR as a novel receptor mediating the sensing of the important skin pathogen S. aureus in keratinocytes.

Bifidobacterium infantis strain YLGB-1496 possesses excellent antioxidant and skin barrier-enhancing efficacy in vitro

Atopic dermatitis (AD) is a recurring allergic skin disease that has a high incidence. Orally applied Bifidobacteria ameliorate signs of irritated skin and enhance the skin barrier. The present study investigated the safety and efficacy of a topically used cell-free culture supernatant (CFS) from a Bifidobacterium infantis strain using in vitro evaluation methods. The results showed that CFS had strong free radical scavenging activity on DPPH, ABTS, ·OH and O₂ -radicals. CFS treatment fundamentally reduced the intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) contents and improved the activities of antioxidant enzymes (CAT, SOD and GSH-Px) in H₂ O₂ -treated HaCaT cells. Notably, the upregulation of skin physical barrier gene (FLG, LOR, IVL, AQP3 and TGM1) expression and skin antimicrobial peptide gene (CAMP, hBD-2 and hBD-3) expression by CFS might contribute to skin barrier resistance. CFS was non-irritating to the skin and eyes. CFS from the Bifidobacterium infantis strain had strong antioxidant properties on the skin and strengthened skin barrier function, and it was safe for topical use.

Potential of Tamanu (Calophyllum inophyllum) Oil for Atopic Dermatitis Treatment

Tamanu oil, derived from the nut of Calophyllum inophyllum L., has been traditionally used to treat various skin-related ailments. In recent years, this oil is increasingly gaining popularity as researchers continue to search for novel natural alternative therapies for various skin diseases. There have been a number of in vitro and in vivo studies investigating various skin-active properties of tamanu oil, and it has been proven to have potent anti-inflammatory, antioxidant, antimicrobial, analgesic, and even wound-healing abilities. These properties make tamanu oil an especially interesting candidate for the treatment of atopic dermatitis (AD). This multifaceted disease is marked by the disruption of the skin barrier function, chronic inflammation, and skin microbiome dysbiosis with limited treatment options, which is free from adverse events and inexpensive, making it desperate for a new treatment option. In this review, we examine previous in vitro and in vivo studies on AD-relevant pharmacological properties of tamanu oil in order to evaluate the potential of tamanu oil as a novel treatment option for AD.

Safety and Danger Considerations of Novel Treatments for Atopic Dermatitis in Context of Primary Cutaneous Lymphomas

The impact of new and emerging therapies on the microenvironment of primary cutaneous lymphomas (PCLs) has been recently raised in the literature. Concomitantly, novel treatments are already used or registered (dupilumab, upadacitinib) and others seem to be added to the armamentarium against atopic dermatitis. Our aim was to review the literature on interleukins 4, 13, 22, and 31, and JAK/STAT pathways in PCLs to elucidate the safety of using biologics (dupilumab, tralokinumab, fezakinumab, nemolizumab) and small molecule inhibitors (upadacitinib, baricitinib, abrocitinib, ruxolitinib, tofacitinib) in the treatment of atopic dermatitis. We summarized the current state of knowledge on this topic based on the search of the PubMed database and related references published before 21 October 2021. Our analysis suggests that some of the mentioned agents (dupilumab, ruxolitinib) and others may have a direct impact on the progression of cutaneous lymphomas. This issue requires further study and meticulous monitoring of patients receiving these drugs to ensure their safety, especially in light of the FDA warning on tofacitinib. In conclusion, in the case of the rapid progression of atopic dermatitis/eczema, especially in patients older than 40 years old, there is a necessity to perform a biopsy followed by a very careful pathological examination.

Free human DNA attenuates the activity of antimicrobial peptides in atopic dermatitis

BACKGROUND

The high susceptibility of AD patients to microbial skin infections has been attributed to a deficient antimicrobial peptide (AMP) expression, which is contradicted by a growing amount of recent studies clearly demonstrating that AMP expression is not impaired in lesional skin of AD patients. The reasons for the high susceptibility of AD patients to microbial infections are still unknown.

METHODS

The influence of self-DNA on the antimicrobial activity of RNase 7, LL-37, and hBD2 has been investigated using antibacterial and antiviral assays. The amount of self-DNA on skin has been analyzed by skin rinsings and subsequent quantification using dsDNA assays. DNA source was identified by qPCR.

RESULTS

Complex formation of the AMPs with self-DNA significantly impaired their antibacterial activity against Staphylococcus aureus and their antiviral activity against HSV-1. The inhibition of the antibacterial activity was dependent on the DNA concentration but not on the length of the DNA molecules. Of note, we detected significant higher amounts of cell-free self-DNA in skin rinses taken from lesional AD skin compared to skin rinses from non-lesional skin and from normal skin of healthy donors. Consequently, rinse solution from AD lesional skin prevented antibacterial activity of LL-37.

CONCLUSION

Our study indicates that extracellular self-DNA is released in considerable amounts in AD skin lesions and AMP-self-DNA-complex formation leads to a significant loss of antibacterial and antiviral activity in atopic dermatitis. Studies on strategies to reduce the amount of extracellular DNA in AD are needed to identify possible methods relevant in clinical settings.

The Keratinocyte as a Crucial Cell in the Predisposition, Onset, Progression, Therapy and Study of the Atopic Dermatitis

The keratinocyte (KC) is the main functional and structural component of the epidermis, the most external layer of the skin that is highly specialized in defense against external agents, prevention of leakage of body fluids and retention of internal water within the cells. Altered epidermal barrier and aberrant KC differentiation are involved in the pathophysiology of several skin diseases, such as atopic dermatitis (AD). AD is a chronic inflammatory disease characterized by cutaneous and systemic immune dysregulation and skin microbiota dysbiosis. Nevertheless, the pathological mechanisms of this complex disease remain largely unknown. In this review, we summarize current knowledge about the participation of the KC in different aspects of the AD. We provide an overview of the genetic predisposing and environmental factors, inflammatory molecules and signaling pathways of the KC that participate in the physiopathology of the AD. We also analyze the link among the KC, the microbiota and the inflammatory response underlying acute and chronic skin AD lesions.

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.

The Role of Antimicrobial Peptides in Preterm Birth

Antimicrobial peptides (AMPs) are short cationic amphipathic peptides with a wide range of antimicrobial properties and play an important role in the maintenance of immune homeostasis by modulating immune responses in the reproductive tract. As intra-amniotic infection and microbial dysbiosis emerge as common causes of preterm births (PTBs), a better understanding of the AMPs involved in the development of PTB is essential. The altered expression of AMPs has been reported in PTB-related clinical presentations, such as preterm labor, intra-amniotic infection/inflammation, premature rupture of membranes, and cervical insufficiency. Moreover, it was previously reported that dysregulation of AMPs may affect the pregnancy prognosis. This review aims to describe the expression of AMPs associated with PTBs and to provide new perspectives on the role of AMPs in PTB.

Biologics for Treatment of Atopic Dermatitis: Current Status and Future Prospect

Atopic dermatitis (AD) is a common inflammatory skin disease characterized by intense pruritus and recurrent eczematous lesions that significantly impair quality of life. It is a heterogeneous disease affecting both children and adults. The treatment of moderate-to-severe forms of AD is challenging, as topical corticosteroids are often insufficient to achieve disease control or inappropriate and off-label use of immunosuppressants may have significant undesirable side effects. The development of targeted biologic therapies specifically for AD is thus highly desirable. Dupilumab is the only biologic therapy that is Food and Drug Administration approved for the treatment of moderate-to-severe AD in patients 6 years and older, with consistent long-term efficacy and safety trial data. In this article, we review the mechanisms, safety, and efficacy of dupilumab from recent clinical trials, and we review the current data, mechanism of action, clinical efficacy, and limitations of new biologics currently in phase 2 and 3 clinical trials (lebrikizumab, tralokinumab, nemolizumab, tezepelumab, and ISB 830).

Brief Academic Review and Clinical Practice Guidelines for Pediatric Atopic Dermatitis

In this clinical guidelines article, we first include a brief review of the epidemiology, pathogenesis, clinical diagnoses, and scoring-scales for pediatric atopic dermatitis (AD). We then offer a set of pharmacologic treatment guidelines for infants and toddlers (<2 years), children (2-12 years), and adolescents (>12 years). We recommend irritant avoidance and liberal emollient usage as the cornerstone of treatment in all age-groups. In infants <2 years, we recommend topical corticosteroids as first-line medication-based therapy. In infants as young as 3 months, pimecrolimus, a topical calcineurin inhibitor, may also be used. As a last resort in patients <2 years, non-traditional therapies, such as the Aron regime, may be a safer option for refractory or resistant AD before off- label medications are considered. In children and adolescents >2 years, topical corticosteroids are still considered first-line therapies, but there is sufficient safety data to utilize topical calcineurin inhibitors and topical PDE4 inhibitors as well. In children ages 2-12 years whose atopic dermatitis fails to respond to prior treatments, oral systemic immunosuppressants can be used. For adolescents >12, the biologic, dupilumab, is an additional therapeutic option. A trial of phototherapy may also be utilized in children, particularly in adolescents >12 years, if they have access to treatment. Although not currently approved for the treatment of AD, Janus-kinase (JAK) inhibitors represent a promising new class of biologics with recently completed phase III clinical trials (JADE-- MONO1/2).

Role of Antimicrobial Peptides in Skin Barrier Repair in Individuals with Atopic Dermatitis

Atopic dermatitis (AD) is a common chronic inflammatory skin disease that exhibits a complex interplay of skin barrier disruption and immune dysregulation. Patients with AD are susceptible to cutaneous infections that may progress to complications, including staphylococcal septicemia. Although most studies have focused on filaggrin mutations, the physical barrier and antimicrobial barrier also play critical roles in the pathogenesis of AD. Within the physical barrier, the stratum corneum and tight junctions play the most important roles. The tight junction barrier is involved in the pathogenesis of AD, as structural and functional defects in tight junctions not only disrupt the physical barrier but also contribute to immunological impairments. Furthermore, antimicrobial peptides, such as LL-37, human b-defensins, and S100A7, improve tight junction barrier function. Recent studies elucidating the pathogenesis of AD have led to the development of barrier repair therapy for skin barrier defects in patients with this disease. This review analyzes the association between skin barrier disruption in patients with AD and antimicrobial peptides to determine the effect of these peptides on skin barrier repair and to consider employing antimicrobial peptides in barrier repair strategies as an additional approach for AD management.

Risk of systemic infections in adults with atopic dermatitis: A nationwide cohort study

BACKGROUND

Atopic dermatitis (AD) has been linked to systemic infections in adulthood, but large-scale studies are few, and potential associations are unclear.

OBJECTIVE

To examine whether adults with AD have increased risk of developing systemic infections leading to hospital-based management.

METHODS

Nationwide register-based cohort study including all Danish adults from 1995 through 2017. Hazard ratios (HRs) with 95% confidence intervals (CIs) were estimated by using Cox models.

RESULTS

A total of 10,602 adults with AD (median age, 29.8 y; interquartile range, 22.6-44.8) and 106,020 reference individuals were included. The overall incidence rate per 10,000 person-years of systemic infections was 180.6 (95% CI, 172.6-189.0) among adults with AD compared with 120.4 (95% CI, 118.3-122.5) among reference adults. The association between AD and systemic infections was observed for musculoskeletal (adjusted HR [aHR], 1.81; 95% CI, 1.42-2.31), heart (aHR, 1.75; 95% CI, 1.21-2.53), and upper (aHR, 1.42; 95% CI, 1.15-1.73) and lower respiratory tract infections (aHR, 1.21; 95% CI, 1.10-1.33). The risk of sepsis (aHR, 1.19; 95% CI, 1.01-1.44) and skin infections (aHR, 2.30; 95% CI, 2.01-2.62) was also increased.

LIMITATIONS

The findings cannot be generalized to adults with milder AD seen outside the hospital system.

CONCLUSION

We found an increased risk of systemic infections among adults with hospital managed AD.

The clinical impact of cross-reactions between allergens on allergic skin diseases

PURPOSE OF REVIEW

The route of allergen sensing via the skin appears to influence the immune system towards mounting a type 2 response, especially in genetically predisposed individuals. Allergens recognized this way may derive from microbial, animal, food, or other plant sources and trigger atopic dermatitis. Allergens can be grouped into families depending on their structure and function, harboring significant structural and sequence similarities. Cross-reactivity between allergens is believed to arise as a consequence, and to underlie the development of further atopic diseases.

RECENT FINDINGS

Especially for the plant allergens of the families of PR10-related proteins and profilins, immune cross-reactions have been described. Actual studies support that food and pollen allergens can aggravate skin lesions in patients suffering from atopic dermatitis. Further on, allergens derived from air-borne or skin-borne fungi belong to common allergen families and bear cross-reactivity potential. Cross-reactivity to human homologous proteins, so-called autoallergens, is discussed to contribute to the chronification of atopic dermatitis.

SUMMARY

Due to high evolutionary conservation, allergic reactions can be triggered by highly homologous members of allergen families on the humoral as well as on the cellular level.

Little Antimicrobial Peptides with Big Therapeutic Roles

Antimicrobial Peptides (AMPs) are short amphipathic biological molecules generally with less than 100 amino acids. AMPs not only present high bioactivities against bacteria, fungi or protists-induced infections, but also play important roles in anticancer activity, immune response and inflammation regulation. AMPs are classified as ribosomally synthesized, non-ribosomally synthesized and post-translationally modified, non-ribosomally synthesized ones and several synthetic or semisynthetic peptides according to their synthesis with or without the involvement of ribosomes. The molecular characterization and bioactivity action mechanisms are summarized for several ribosomally synthesized AMPs and main non-ribosomally synthesized members (cyclopeptides, lipopeptides, glycopeptides, lipoglycopeptides). We also analyze challenges and new strategies to overcome drug resistance and application limitations for AMP discovery. In conclusion, the growing novel small molecular AMPs have huge therapeutic potentials of antibacterial, antiviral, anticancer and immunoregulatory bioactivities through new techniquesdriven drug discovery strategy including bioinformatics prediction, de novo rational design and biosynthesis.

[Pathogenesis of atopic dermatitis]

Atopic dermatitis (AD) is one of the most common chronic inflammatory diseases and is also one of the most frequent reasons to consult a dermatologist. Over the past few years there has been a rapidly growing understanding of the cellular, molecular and immunological relationships as well as genetic variations, which leads to a better comprehension of the disease. Consequently, there are innovative targeted therapies in clinical studies or already approved for therapy. To make reasonable use of the new targeted therapies a good understanding of the pathogenesis is very important. In the future, stratification of patients with AD and the resulting personalized therapies will gain in importance. This review depicts the up to date state of knowledge on the complex pathogenesis of AD.

A topical treatment containing heat-treated Lactobacillus johnsonii NCC 533 reduces Staphylococcus aureus adhesion and induces antimicrobial peptide expression in an in vitro reconstructed human epidermis model

Staphylococcus aureus colonization is thought to contribute to the pathophysiology of atopic dermatitis (AD). AD patients exhibit reduced levels of cutaneous antimicrobial peptides (AMPs), which may explain their increased susceptibility to infections. Using an in vitro reconstructed human epidermis (RHE) model, we sought to determine whether topical application of a non-replicating probiotic, heat-treated Lactobacillus johnsonii NCC 533 (HT La1), could inhibit S. aureus adhesion to skin and boost cutaneous innate immunity. We found that application of HT La1 suspension to RHE samples reduced the binding of radiolabelled S. aureus by up to 74%. To investigate a potential effect of HT La1 on innate immunity, we analysed the expression of nine AMP genes, including those encoding beta defensins and S100 proteins, following topical application of HT La1 in suspension or in a daily moisturizer lotion. Analysed genes were induced by up to fourfold in a dose-dependent manner by HT La1 in suspension and by up to 2.4-fold by HT La1 in the moisturizer lotion. Finally, using ELISA and immunohistochemical detection, we evaluated the expression and secretion of the AMPs hBD-2 and psoriasin and determined that both proteins were induced by topical HT La1, particularly in the stratum corneum of the RHE. These findings demonstrate that a topically applied, non-replicating probiotic can modulate endogenous AMP expression and inhibit binding of S. aureus to an RHE model in vitro. Moreover, they suggest that a topical formulation containing HT La1 could benefit atopic skin by enhancing cutaneous innate immunity and reducing S. aureus colonization.

Atopic dermatitis: the skin barrier and beyond

BACKGROUND

Atopic dermatitis is the most common chronic inflammatory skin disorder, affecting up to 20% of children and 10% of adults in industrialized countries. This highly debilitating condition poses a considerable burden to both the individual and society at large. The pathophysiology of atopic dermatitis is complex, encompassing both genetic and environmental risk factors.

METHODS

This is a narrative review based on a systematic literature search.

CONCLUSIONS

Dysregulation of innate and adaptive immunity plays a key role; however, recent epidemiological, genetic and molecular research has focused interest on skin barrier dysfunction as a common precursor and pathological feature. Current understanding of the aetiology of atopic dermatitis highlights disruption of the epidermal barrier leading to increased permeability of the epidermis, pathological inflammation in the skin, and percutaneous sensitization to allergens. Thus, most novel treatment strategies seek to target specific aspects of the skin barrier or cutaneous inflammation. Several studies have also shown promise in preventing atopic dermatitis, such as the early use of emollients in high-risk infants. This may have broader implications in terms of halting the progression to atopic comorbidities including food allergy, hay fever and asthma.

RNase 7 participates in cutaneous innate control of Corynebacterium amycolatum

Nondiphtheria corynebacteria are typical members of the skin microbiota. However, in addition to being harmless inhabitants of healthy skin commensal skin-derived corynebacteria such as C. amycolatum occasionally also cause infections. This suggests that human skin must harbor adequate mechanisms to control the growth of corynebacteria on the skin surface. Here we show that keratinocytes are able to detect the presence of C. amycolatum leading to the epidermal growth factor receptor (EGFR)-dependent induction of the antimicrobial protein RNase 7. C. amycolatum-mediated induction of RNase 7 was also confirmed in a human 3D skin equivalent. The functional relevance of these findings was demonstrated by potent antimicrobial activity of RNase 7 against C. amycolatum and C. xerosis. In addition, the capacity of human stratum corneum to restrict the growth of C. amycolatum was significantly attenuated when RNase 7 was inactivated by a specific RNase 7-neutralizing antibody. Taken together, the interaction of RNase 7 with C. amycolatum indicates that RNase 7 may function as important effector molecule to control the growth of corynebacteria on human skin.

Is cathelicidin a novel marker of diabetic microangiopathy in patients with type 1 diabetes?

AIM

The aim was to evaluate the relationship between higher serum cathelicidin levels with the occurrence of chronic microangiopathic complications in patients with diabetes mellitus type 1 (DM1).

METHODS

The study group consisted of 62 patients with DM1 (35 men), aged 30 (24-38) years and with duration of DM1 12 (9-17) years. Patients were divided into two groups depending on the level of cathelicidin, with cut-off point 24.5ng/ml (median value for the whole group) and according to the presence or absence of any microangiopathy.

RESULTS

The group with higher serum level of cathelicidin (n=31) in comparison with patients with lower levels (n=31) had higher serum level of total cholesterol [5.0(4.5-5.6) vs 4.5(3.9-5.0) mmol/l; p=0.04], HDL cholesterol [1.9(1.5-2.1) vs 1.4(1.3-1.8) mmol/l; p=0.009], LDL cholesterol [2.6(2.2-3.1) vs 2.3(1.9-2.8) mmol/l; p=0.03] and higher TSH value [1.8(1.5-2.6) vs 1.4(0.9-2.1) mIU/L; p=0.01]. Moreover, higher serum levels of cathelicidin were in women than men (58% vs 29%, p=0.02) and in patients with vs without microangiopathy (45% vs 19%, p=0.03). In the multiple regression model higher serum level of cathelicidin was related to the presence of microangiopathy, independently from sex, waist to hip ratio, serum total cholesterol level and TSH.

CONCLUSIONS

Patients with type 1 diabetes and presence of microangiopathy characterize higher level of serum cathelicidin. This observation may have important clinical implication and needs further investigations.

Cellular and molecular immunologic mechanisms in patients with atopic dermatitis

Atopic dermatitis (AD) is a complex skin disease frequently associated with other diseases of the atopic diathesis. Recent evidence supports the concept that AD can also recognize other comorbidities, such as chronic inflammatory bowel or cardiovascular diseases. These comorbidities might result from chronic cutaneous inflammation or from a common, yet-to-be-defined immunologic background leading to immune deviations. The activation of immune cells and their migration to the skin play an essential role in the pathogenesis of AD. In patients with AD, an underlying immune deviation might result in higher susceptibility of the skin to environmental factors. There is a high unmet medical need to define immunologic endotypes of AD because it has significant implications on upcoming stratification of the phenotype of AD and the resulting targeted therapies in the development of precision medicine. This review article emphasizes studies on environmental factors affecting AD development and novel biological agents used in the treatment of AD. Best evidence of the clinical efficacy of novel immunologic approaches using biological agents in patients with AD is available for the anti-IL-4 receptor α-chain antibody dupilumab, but a number of studies are currently ongoing with other specific antagonists to immune system players. These targeted molecules can be expressed on or drive the cellular players infiltrating the skin (eg, T lymphocytes, dendritic cells, or eosinophils). Such approaches can have immunomodulatory and thereby beneficial clinical effects on the overall skin condition, as well as on the underlying immune deviation that might play a role in comorbidities. An effect of these immunologic treatments on pruritus and the disturbed microbiome in patients with AD has other potential consequences for treatment.

Emerging concepts: mast cell involvement in allergic diseases

In a process known as overt degranulation, mast cells can release all at once a diverse array of products that are preformed and present within cytoplasmic granules. This occurs typically within seconds of stimulation by environmental factors and allergens. These potent, preformed mediators (ie, histamine, heparin, serotonin, and serine proteases) are responsible for the acute symptoms experienced in allergic conditions such as allergic conjunctivitis, allergic rhinitis, allergy-induced asthma, urticaria, and anaphylaxis. Yet, there is reason to believe that the actions of mast cells are important when they are not degranulating. Mast cells release preformed mediators and inflammatory cytokines for periods after degranulation and even without degranulating at all. Mast cells are consistently seen at sites of chronic inflammation, including nonallergic inflammation, where they have the ability to temper inflammatory processes and shape tissue morphology. Mast cells can trigger actions and chemotaxis in other important immune cells (eg, eosinophils and the newly discovered type 2 innate lymphocytes) that then make their own contributions to inflammation and disease. In this review, we will discuss the many known and theorized contributions of mast cells to allergic diseases, focusing on several prototypical allergic respiratory and skin conditions: asthma, chronic rhinosinusitis, aspirin-exacerbated respiratory disease, allergic conjunctivitis, atopic dermatitis, and some of the more common medication hypersensitivity reactions. We discuss traditionally accepted roles that mast cells play in the pathogenesis of each of these conditions, but we also delve into new areas of discovery and research that challenge traditionally accepted paradigms.

RNase 7 in Cutaneous Defense

RNase 7 belongs to the RNase A superfamily and exhibits a broad spectrum of antimicrobial activity against various microorganisms. RNase 7 is expressed in human skin, and expression in keratinocytes can be induced by cytokines and microbes. These properties suggest that RNase 7 participates in innate cutaneous defense. In this review, we provide an overview about the role of RNase 7 in cutaneous defense with focus on the molecular mechanism of the antimicrobial activity of RNase 7, the regulation of RNase 7 expression, and the role of RNase 7 in skin diseases.

Atopic dermatitis

Atopic dermatitis (also known as atopic eczema) is a chronic inflammatory skin disease that is characterised by intense itching and recurrent eczematous lesions. Although it most often starts in infancy and affects two of ten children, it is also highly prevalent in adults. It is the leading non-fatal health burden attributable to skin diseases, inflicts a substantial psychosocial burden on patients and their relatives, and increases the risk of food allergy, asthma, allergic rhinitis, other immune-mediated inflammatory diseases, and mental health disorders. Originally regarded as a childhood disorder mediated by an imbalance towards a T-helper-2 response and exaggerated IgE responses to allergens, it is now recognised as a lifelong disposition with variable clinical manifestations and expressivity, in which defects of the epidermal barrier are central. Present prevention and treatment focus on restoration of epidermal barrier function, which is best achieved through the use of emollients. Topical corticosteroids are still the first-line therapy for acute flares, but they are also used proactively along with topical calcineurin inhibitors to maintain remission. Non-specific immunosuppressive drugs are used in severe refractory cases, but targeted disease-modifying drugs are being developed. We need to improve understanding of the heterogeneity of the disease and its subtypes, the role of atopy and autoimmunity, the mechanisms behind disease-associated itch, and the comparative effectiveness and safety of therapies.

Plasma α-defensins are elevated during exacerbation of atopic dermatitis

BACKGROUND

There is no currently no information regarding the role of α-defensins in the pathophysiology of atopic dermatitis (AD).

AIM

To investigate levels of plasma α-defensins at exacerbation and remission of AD, and to assess their association with clinical severity of AD.

METHODS

Patients with AD during exacerbation were recruited from the Dermatology department at the Chita Medical Academy (Chita, Russian Federation). SCORAD (SCORing Atopic Dermatitis), itch intensity, plasma concentrations of α-defensins, and serum total IgE, interleukin (IL)-1β, IL-8 and IL-10 levels were measured at study entry and after 4 months.

RESULTS

In total, 82 patients with AD [35 (45.1%) female and 47 (54.9%) male patients, mean ± SD age 42.2 ± 11.5 years, range 15-40] and 30 healthy controls (HCs) were included. Mean objective SCORAD score was 48.8 ± 19.4 and 16.1 ± 8.3 during AD during exacerbation and remission, respectively (P < 0.01). Plasma α-defensin levels in patients with AD (1.41 ± 0.32 μg/L) were significantly higher than in HCs (0.91 ± 0.34 μg/L) (P < 0.001). Significant correlations were found between plasma α-defensin levels with objective SCORAD (r = 0.55, P < 0.001), itch severity (r = 0.25, P < 0.05) and serum IgE levels (r = 0.38, P < 0.001) during AD exacerbation. Serum concentrations of IL-1β, IL-4 and IL-8 were significantly higher and levels of IL-10 were lower at AD exacerbation in patients than in HCs, with a weak negative correlation between plasma α-defensin and serum IL-10 levels (r = -0.22; P < 0.05).

CONCLUSION

During AD exacerbation, plasma α-defensin levels are elevated, and are positively correlated with AD clinical severity, itch intensity and serum IgE levels.

Intraindividual genome expression analysis reveals a specific molecular signature of psoriasis and eczema

Previous attempts to gain insight into the pathogenesis of psoriasis and eczema by comparing their molecular signatures were hampered by the high interindividual variability of those complex diseases. In patients affected by both psoriasis and nonatopic or atopic eczema simultaneously (n = 24), an intraindividual comparison of the molecular signatures of psoriasis and eczema identified genes and signaling pathways regulated in common and exclusive for each disease across all patients. Psoriasis-specific genes were important regulators of glucose and lipid metabolism, epidermal differentiation, as well as immune mediators of T helper 17 (TH17) responses, interleukin-10 (IL-10) family cytokines, and IL-36. Genes in eczema related to epidermal barrier, reduced innate immunity, increased IL-6, and a TH2 signature. Within eczema subtypes, a mutually exclusive regulation of epidermal differentiation genes was observed. Furthermore, only contact eczema was driven by inflammasome activation, apoptosis, and cellular adhesion. On the basis of this comprehensive picture of the pathogenesis of psoriasis and eczema, a disease classifier consisting of NOS2 and CCL27 was created. In an independent cohort of eczema (n = 28) and psoriasis patients (n = 25), respectively, this classifier diagnosed all patients correctly and also identified initially misdiagnosed or clinically undifferentiated patients.

Mast cells and basophils in cutaneous immune responses

Mast cells and basophils share some functions in common and are generally associated with T helper 2 (Th2) immune responses, but taking basophils as surrogate cells for mast cell research or vice versa for several decades is problematic. Thus far, their in vitro functions have been well studied, but their in vivo functions remained poorly understood. New research tools for their functional analysis in vivo have revealed previously unrecognized roles for mast cells and basophils in several skin disorders. Newly developed mast cell-deficient mice provided evidence that mast cells initiate contact hypersensitivity via activating dendritic cells. In addition, studies using basophil-deficient mice have revealed that basophils were responsible for cutaneous Th2 skewing to haptens and peptide antigens but not to protein antigens. Moreover, human basophils infiltrate different skin lesions and have been implicated in the pathogenesis of skin diseases ranging from atopic dermatitis to autoimmune diseases. In this review, we will discuss the recent advances related to mast cells and basophils in human and murine cutaneous immune responses.

Impaired NLRP3 inflammasome expression and function in atopic dermatitis due to Th2 milieu

BACKGROUND

Atopic dermatitis (AD) and psoriasis patients are frequently colonized with Staphylococcus aureus (S. aureus) that produce the staphylococcal exotoxin α-toxin. However, only patients with AD suffer from bacterial superinfections with this pathogen, which implicates immunological differences in AD vs psoriasis in combating these bacteria. S. aureus recognition is partially mediated by intracellular nucleotide-binding oligomerization domain receptors (NLRs), which link α-toxin to caspase-1 activation through the formation of the NLRP3 inflammasome and to IL-1β secretion.

OBJECTIVE

To investigate (i) NLRP3 expression in the context of different T-helper cytokine milieus and (ii) its function in response to sublytic α-toxin stimulation in patients with AD and psoriasis compared with healthy controls.

METHODS

NLRP3 expression and function were investigated in lesional AD and psoriasis skin as well as in primary keratinocytes (HPKs) and monocytes upon stimulation with Th1, Th2, Th17 and Th22 cytokines or staphylococcal α-toxin, respectively, at the mRNA and protein (ELISA, immunohistochemistry and immunofluorescence) level.

RESULTS

NLRP3 and caspase-1 expressions were reduced in lesional AD skin compared to psoriatic and healthy skin. IL-4, IL-5 and IL-13 downregulated NLRP3 and ASC, whereas interferon-γ upregulated NLRP3 in HPKs. In monocytes, caspase-1 expression was reduced by Th2 cytokines and enhanced by a Th1 milieu. Caspase-1-dependent IL-1β secretion was impaired in monocytes from patients with AD compared to patients with psoriasis and healthy controls by α-toxin stimulation following priming with lipoteichoic acid.

CONCLUSION

Impaired NLRP3 expression and function may partially explain how skin colonization and infection with S. aureus can contribute to chronic skin inflammation in AD.

Skin barrier dysfunction and low antimicrobial peptide expression in cutaneous T-cell lymphoma

PURPOSE

Atopic dermatitis is characterized by decreased expression of filaggrin and loricrin. Patients with atopic dermatitis often suffer from skin infections, which are also frequently seen in patients with cutaneous T-cell lymphoma (CTCL). In this study, we aimed to investigate the skin barrier in CTCL.

EXPERIMENTAL DESIGN

We assessed skin moisture and transepidermal water loss (TEWL) in patients with CTCL. We next examined mRNA expression levels of filaggrin, loricrin, and antimicrobial peptides (AMP) in skin samples of CTCL, using skin from healthy volunteers and patients with atopic dermatitis or psoriasis as controls. Immunostainings for filaggrin, loricrin, and S100 proteins were also performed.

RESULTS

Lower levels of skin moisture accompanied by higher levels of TEWL were seen in lesional skin of CTCL than in normal skin. CTCL lesional skin contained lower levels of filaggrin and loricrin mRNA than normal skin, which was also true with atopic dermatitis and psoriatic skin. mRNA expression levels of filaggrin in CTCL skin negatively correlated with disease severity markers. Expression levels of AMPs in lesional skin of CTCL and atopic dermatitis were significantly lower than in psoriatic skin. Immunohistochemistry confirmed decreased expression of filaggrin and loricrin in CTCL, atopic dermatitis, and psoriatic skin and enhanced expression of S100 proteins in psoriatic skin.

CONCLUSIONS

Our results show that there is barrier dysfunction in CTCL skin, similar to what is seen with atopic dermatitis skin. In addition, low AMP expression in CTCL skin was documented when compared with psoriatic skin, which may explain frequent infections that can occur in patients with CTCL.

Epidermal permeability barrier defects and barrier repair therapy in atopic dermatitis

Atopic dermatitis (AD) is a multifactorial inflammatory skin disease perpetuated by gene-environmental interactions and which is characterized by genetic barrier defects and allergic inflammation. Recent studies demonstrate an important role for the epidermal permeability barrier in AD that is closely related to chronic immune activation in the skin during systemic allergic reactions. Moreover, acquired stressors (e.g., Staphylococcus aureus infection) to the skin barrier may also initiate inflammation in AD. Many studies involving patients with AD revealed that defective skin barriers combined with abnormal immune responses might contribute to the pathophysiology of AD, supporting the outside-inside hypothesis. In this review, we discuss the recent advances in human and animal models, focusing on the defects of the epidermal permeability barrier, its immunologic role and barrier repair therapy in AD.