Endogenous antimicrobial peptides and skin infections in atopic dermatitis

Changes in Gut Microbiota Correlates with Response to Treatment with Probiotics in Patients with Atopic Dermatitis. A Post Hoc Analysis of a Clinical Trial

Atopic dermatitis (AD) is a chronic recurrent inflammatory skin disease with a high impact on the comfort of those who are affected and long-term treated with corticosteroids with limited efficacy and a high prevalence of relapses. Because of the limited effectiveness of these treatments, new strategies for recovery from AD lesions are continually being explored. In this article, we describe the gut microbiome changes achieved in a recently published clinical trial with the probiotic formulation Bifidobacterium animalis subsp. lactis CECT 8145, Bifidobacterium longum CECT 7347, and Lacticaseibacillus casei CECT 9104 (formerly Lactobacillus casei CECT 9104), showing a significant improvement in SCORAD (scoring atopic dermatitis) index in children (4-17 years) with AD (Clinicaltrials.gov identifier: NCT02585986). The present gut microbiome post hoc study showed no significant changes in diversity (Shannon and Simpson indexes) after probiotic consumption. In the probiotic group, genera Bacteroides, Ruminococcus, and Bifidobacterium significantly increased their levels while Faecalibacterium decreased, compared to the placebo group. Faecalibacterium showed the highest presence and significant positive correlation with AD severity (SCORAD index), whereas Abyssivirga, Bifidobacterium, and Lactococcus were inversely correlated. The results suggest that the consumption of the probiotic formulation here assayed modulates the gut microbiome with significant changes in genera Bacteroides and Faecalibacterium. In turn, the improvement in SCORAD correlates with a decrease in Faecalibacterium and an increase in Bifidobacterium, among others.

Development of a human skin commensal microbe for bacteriotherapy of atopic dermatitis and use in a phase 1 randomized clinical trial

Staphylococcus aureus colonizes patients with atopic dermatitis (AD) and exacerbates disease by promoting inflammation. The present study investigated the safety and mechanisms of action of Staphylococcus hominis A9 (ShA9), a bacterium isolated from healthy human skin, as a topical therapy for AD. ShA9 killed S. aureus on the skin of mice and inhibited expression of a toxin from S. aureus (psmα) that promotes inflammation. A first-in-human, phase 1, double-blinded, randomized 1-week trial of topical ShA9 or vehicle on the forearm skin of 54 adults with S. aureus-positive AD (NCT03151148) met its primary endpoint of safety, and participants receiving ShA9 had fewer adverse events associated with AD. Eczema severity was not significantly different when evaluated in all participants treated with ShA9 but a significant decrease in S. aureus and increased ShA9 DNA were seen and met secondary endpoints. Some S. aureus strains on participants were not directly killed by ShA9, but expression of mRNA for psmα was inhibited in all strains. Improvement in local eczema severity was suggested by post-hoc analysis of participants with S. aureus directly killed by ShA9. These observations demonstrate the safety and potential benefits of bacteriotherapy for AD.

Cutaneous antimicrobial peptides: New "actors" in pollution related inflammatory conditions

Ozone (O₃) exposure has been reported to contribute to various cutaneous inflammatory conditions, such as eczema, psoriasis, rush etc. via a redox-inflammatory pathway. O₃ is too reactive to penetrate cutaneous tissue; it interacts with lipids present in the outermost layer of skin, resulting in formation of oxidized molecules and hydrogen peroxide (H₂O₂). Interestingly, several inflammatory skin pathologies demonstrate altered levels of antimicrobial peptides (AMPs). These small, cationic peptides are found in various cells, including keratinocytes, eccrine gland cells, and seboctyes. Classically, AMPs function as antimicrobial agents. Recent studies indicate that AMPs also play roles in inflammation, angiogenesis, and wound healing. Since altered levels of AMPs have been detected in pollution-associated skin pathologies, we hypothesized that exposure to O₃ could affect the levels of AMPs in the skin. We examined levels of AMPs using qRT-PCR, Western blotting, and immunofluorescence in vitro (human keratinocytes), ex vivo (human skin explants), and in vivo (human volunteer subjects exposed to O₃) and observed increased levels of all the measured AMPs upon O₃ exposure. In addition, in vitro studies have confirmed the redox regulation of AMPs in keratinocytes. This novel finding suggests that targeting AMPs could be a possible defensive strategy to combat pollution-associated skin conditions.

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AMPs (hBDs1-3, CAMP) increase in O₃ exposed human skin by a redox mechanism.

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Transcriptional upregulation of AMPs in response to O₃ exposure is due to an altered redox status.

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Pollution increase AMPs could be the connection between pollution exposure and the development/exacerbation of inflammatory skin conditions.

Interferon-Lambda 1 Inhibits Staphylococcus aureus Colonization in Human Primary Keratinocytes

Atopic dermatitis (AD) is a common inflammatory skin disease. Staphylococcus aureus (S. aureus) colonization in skin lesions occurs in approximately 70% of AD patients. It has been found that IFN-λ1 can inhibit the colonization of S. aureus in normal human nasal mucosa. IFN-λ1 can increase IL-28RA in infected human keratinocytes. In this study, we found that IFN-λ1 can increase mRNA expression of FLG and antimicrobial peptides (AMPs) and inhibit TSLP mRNA expression in infected human keratinocytes. IFN-λ1 can increase intracellular ROS level, decrease STAT1 phosphorylation, and inhibit the colonization of S. aureus in human primary keratinocytes. These effects were attenuated by knocking-down IL-28R and NADPH oxidase inhibitor, suggesting that this function was mediated by JAK-STAT1 signaling pathway. These results suggest that IFN-λ1 might have an inhibitory effect on S. aureus colonization in AD lesions. Our findings might have potential value in the treatment for AD.

Modulation of Human Beta-Defensin 2 Expression by Pathogenic Neisseria meningitidis and Commensal Lactobacilli

Antimicrobial peptides (AMPs) play an important role in the defense against pathogens by targeting and killing invading microbes. Some pathogenic bacteria have been shown to negatively regulate AMP expression, while several commensals may induce AMP expression. The expression of certain AMPs, such as human beta-defensin 2 (hBD2), can be induced via nuclear factor NF-κB, which, in turn, is negatively controlled by tumor necrosis factor alpha-induced protein 3 (TNFAIP3, or A20). In this work, we examined the expression of hBD1 and hBD2 during coincubation of pharyngeal epithelial cells with pathogenic Neisseria meningitidis and commensal lactobacilli. The Lactobacillus strains induced hBD2 expression in human pharyngeal cells, while the pathogen N. meningitidis did not. In coincubation experiments, meningococci were able to dampen the AMP expression induced by lactobacilli. We found that N. meningitidis induced the NF-κB inhibitor A20. Further, RNA silencing of A20 resulted in increased hBD2 expression after meningococcal infection. Since it is known that induction of A20 reduces NF-κB activity and thus hBD2 levels, meningococcal-mediated A20 induction could be a way for the pathogen to dampen AMP expression. Finally, treatment of N. meningitidis and lactobacilli with synthetic hBD2 reduced N. meningitidis viability more efficiently than Lactobacillus reuteri, explaining why maintaining low AMP levels is important for the survival of the pathogen.

The role of lactobacilli in inhibiting skin pathogens

The human skin microbiota forms a key barrier against skin pathogens and is important in modulating immune responses. Recent studies identify lactobacilli as endogenous inhabitants of healthy skin, while inflammatory skin conditions are often associated with a disturbed skin microbiome. Consequently, lactobacilli-based probiotics are explored as a novel treatment of inflammatory skin conditions through their topical skin application. This review focuses on the potential beneficial role of lactobacilli (family Lactobacillaceae) in the skin habitat, where they can exert multifactorial local mechanisms of action against pathogens and inflammation. On one hand, lactobacilli have been shown to directly compete with skin pathogens through adhesion inhibition, production of antimicrobial metabolites, and by influencing pathogen metabolism. The competitive anti-pathogenic action of lactobacilli has already been described mechanistically for common different skin pathogens, such as Staphylococcus aureus, Cutibacterium acnes, and Candida albicans. On the other hand, lactobacilli also have an immunomodulatory capacity associated with a reduction in excessive skin inflammation. Their influence on the immune system is mediated by bacterial metabolites and cell wall-associated or excreted microbe-associated molecular patterns (MAMPs). In addition, lactobacilli can also enhance the skin barrier function, which is often disrupted as a result of infection or in inflammatory skin diseases. Some clinical trials have already translated these mechanistic insights into beneficial clinical outcomes, showing that topically applied lactobacilli can temporarily colonize the skin and promote skin health, but more and larger clinical trials are required to generate in vivo mechanistic insights and in-depth skin microbiome analysis.

Dental Caries in Adults with Atopic Dermatitis: A Nationwide Cross-Sectional Study in Korea

Background

Dental caries is the most prevalent chronic infectious oral disease of multifactorial etiology. Increased risk of dental caries development in patients with asthma and allergic rhinitis has been frequently reported. In contrast, only a few studies on dental caries in patients with atopic dermatitis (AD) have been reported.

Objective

We investigated the association between AD and dental caries development in an adult population in the Republic of Korea.

Methods

A total of 21,606 adults who participated in the Korean National Health and Nutrition Examination Survey, a nationwide, population-based, cross-sectional survey between 2010 and 2015, were included in the study. Multiple logistic regression analyses with confounder adjustment suggested odds ratios (ORs) to identify the possible association between AD and decayed, missing, filled teeth (DMFT) experience compared to non-AD participants. Multiple Poisson regression analyses estimated the mean ratio of the DMFT index according to the presence of AD.

Results

After adjusting for various confounding factors, the prevalence of DMFT was significantly associated with AD (OR, 1.58; 95% confidence interval (CI), 1.08~2.29; p=0.017). In addition, the mean value of the DMFT index was significantly different between the AD and non-AD groups (mean ratio, 1.07; 95% CI, 1.00~1.14; p=0.046).

Conclusion

AD was significantly associated with the development of dental caries. Dermatologists should be aware of the dental manifestations of AD patients and recommend regular dental check-ups for the early detection of caries.

Intractable Itch in Atopic Dermatitis: Causes and Treatments

Itch or pruritus is the hallmark of atopic dermatitis and is defined as an unpleasant sensation that evokes the desire to scratch. It is also believed that itch is a signal of danger from various environmental factors or physiological abnormalities. Because histamine is a well-known substance inducing itch, H₁-antihistamines are the most frequently used drugs to treat pruritus. However, H₁-antihistamines are not fully effective against intractable itch in patients with atopic dermatitis. Given that intractable itch is a clinical problem that markedly decreases quality of life, its treatment in atopic dermatitis is of high importance. Histamine-independent itch may be elicited by various pruritogens, including proteases, cytokines, neuropeptides, lipids, and opioids, and their cognate receptors, such as protease-activated receptors, cytokine receptors, Mas-related G protein-coupled receptors, opioid receptors, and transient receptor potential channels. In addition, cutaneous hyperinnervation is partly involved in itch sensitization in the periphery. It is believed that dry skin is a key feature of intractable itch in atopic dermatitis. Treatment of the underlying conditions that cause itch is necessary to improve the quality of life of patients with atopic dermatitis. This review describes current insights into the pathophysiology of itch and its treatment in atopic dermatitis.

Role of the IL-23/IL-17 Pathway in Rheumatic Diseases: An Overview

Interleukin-23 (IL-23) is a pro-inflammatory cytokine composed of two subunits, IL-23A (p19) and IL-12/23B (p40), the latter shared with Interleukin-12 (IL-12). IL-23 is mainly produced by macrophages and dendritic cells, in response to exogenous or endogenous signals, and drives the differentiation and activation of T helper 17 (Th17) cells with subsequent production of IL-17A, IL-17F, IL-6, IL-22, and tumor necrosis factor α (TNF-α). Although IL-23 plays a pivotal role in the protective immune response to bacterial and fungal infections, its dysregulation has been shown to exacerbate chronic immune-mediated inflammation. Well-established experimental data support the concept that IL-23/IL-17 axis activation contributes to the development of several inflammatory diseases, such as PsA, Psoriasis, Psoriatic Arthritis; AS, Ankylosing Spondylitis; IBD, Inflammatory Bowel Disease; RA, Rheumatoid Arthritis; SS, Sjogren Syndrome; MS, Multiple Sclerosis. As a result, emerging clinical studies have focused on the blockade of this pathogenic axis as a promising therapeutic target in several autoimmune disorders; nevertheless, a greater understanding of its contribution still requires further investigation. This review aims to elucidate the most recent studies and literature data on the pathogenetic role of IL-23 and Th17 cells in inflammatory rheumatic diseases.

Cutaneous barrier dysfunction in allergic diseases

The fundamental defect(s) that drives atopic dermatitis (AD) remains controversial. "Outside in" proponents point to the important association of filaggrin gene mutations and other skin barrier defects with AD. The "inside out" proponents derive support from evidence that AD occurs in genetic animal models with overexpression of type 2 immune pathways in their skin, and humans with gain-of-function mutations in their type 2 response develop severe AD. The observation that therapeutic biologics, targeting type 2 immune responses, can reverse AD provides compelling support for the importance of "inside out" mechanisms of AD. In this review, we propose a central role for epithelial cell dysfunction that accounts for the dual role of skin barrier defects and immune pathway activation in AD. The complexity of AD has its roots in the dysfunction of the epithelial barrier that allows the penetration of allergens, irritants, and microbes into a cutaneous milieu that facilitates the induction of type 2 immune responses. The AD phenotypes and endotypes that result in chronic skin inflammation and barrier dysfunction are modified by genes, innate/adaptive immune responses, and different environmental factors that cause skin barrier dysfunction. There is also compelling evidence that skin barrier dysfunction can alter the course of childhood asthma, food allergy, and allergic rhinosinusitis. Effective management of AD requires a multipronged approach, not only restoring cutaneous barrier function, microbial flora, and immune homeostasis but also enhancing skin epithelial differentiation.

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.

Immunological Roles of NLR in Allergic Diseases and Its Underlying Mechanisms

Our understanding on the immunological roles of pathogen recognition in innate immunity has vastly increased over the past 20 years. Nucleotide-binding oligomerization domain (NOD)-like receptors (NLR) are cytosolic pattern recognition receptors (PRR) that are responsible for sensing microbial motifs and endogenous damage signals in mammalian cytosol for immune surveillance and host defense. The accumulating discoveries on these NLR sensors in allergic diseases suggest that the pathogenesis of allergic diseases may not be confined to the adaptive immune response. Therapy targeting NLR in murine models also shields light on its potential in the treatment of allergies in man. In this review, we herein summarize the recent understanding of the role of NLR sensors and their molecular mechanisms involved in allergic inflammation, including atopic dermatitis and allergic asthma.

SMOC1 and IL-4 and IL-13 Cytokines Interfere with Ca2+ Mobilization in Primary Human Keratinocytes

Immunoregulatory effects of IL-4 and IL-13 and alterations of keratinocyte (KC) differentiation are important factors in the pathogenesis of atopic dermatitis. This study investigated the role of IL-4 and IL-13 in KC responses to changes in extracellular calcium (Ca²⁺) and analyzed differentiation signals elicited via a Ca²⁺ sensor, SMOC1. Real-time dynamics of transmembrane Ca²⁺ influx were assessed in live KCs by flow cytometry and microscopy. Exposure of KCs to a high Ca²⁺ environment (1.3 mM) triggered a rapid intracellular Ca²⁺ influx, whereas IL-4- and IL-13-treated cells exhibited a significant decrease in the peak amplitude of Ca²⁺ influx (P < 0.01). IL-17A and IL-22 did not elicit such responses. Evaluation of intracellular Ca²⁺ dynamics by microscopy confirmed these observations and revealed heterogeneity of individual KC responses. IL-4 and IL-13 significantly inhibited the expression of Ca²⁺-binding protein SMOC1 (P < 0.001). Inhibition of epidermal differentiation markers were also observed in SMOC1 small interfering RNA-transfected KCs. Concurrently, the deletion of SMOC1 increased the amplitude of Ca²⁺ peak response (P < 0.05). In conclusion, our results provide innovative data that IL-4 and IL-13 regulate KC sensitivity to microenvironmental Ca²⁺ changes and inhibit Ca²⁺-induced KC differentiation signals. SMOC1 inhibition by IL-4 and IL-13 alters Ca²⁺ transport in KCs and inhibits differentiation, suggesting a new target for treatment of atopic dermatitis.

Host Responses in an Ex Vivo Human Skin Model Challenged With Malassezia sympodialis

Malassezia species are a major part of the normal mycobiota and colonize mainly sebum-rich skin regions of the body. This group of fungi cause a variety of infections such as pityriasis versicolor, folliculitis, and fungaemia. In particular, Malassezia sympodialis and its allergens have been associated with non-infective inflammatory diseases such as seborrheic dermatitis and atopic eczema. The aim of this study was to investigate the host response to M. sympodialis on oily skin (supplemented with oleic acid) and non-oily skin using an ex vivo human skin model. Host-pathogen interactions were analyzed by SEM, histology, gene expression, immunoassays and dual species proteomics. The skin response to M. sympodialis was characterized by increased expression of the genes encoding β-defensin 3 and RNase7, and by high levels of S100 proteins in tissue. Supplementation of oleic acid onto skin was associated with direct contact of yeasts with keratinocytes and epidermal damage. In oily conditions, there was increased expression of IL18 but no expression of antimicrobial peptide genes in the skin’s response to M. sympodialis. In supernatants from inoculated skin plus oleic acid, TNFα, IL-6, and IL1-β levels were decreased and IL-18 levels were significantly increased.

Exogenous factors in the pathogenesis of atopic dermatitis: Irritants and cutaneous infections

Atopic dermatitis (AD) is a chronic relapsing inflammatory cutaneous disease that is often associated with other atopic symptoms, such as food allergy, allergic rhinitis and asthma, leading to significant morbidity and healthcare costs. The pathogenesis of AD is complicated and multifactorial. Although the aetiology of AD remains incompletely understood, recent studies have provided further insight into AD pathophysiology, demonstrating that the interaction among genetic predisposition, immune dysfunction and environmental provocation factors contributes to its development. However, the increasing prevalence of AD suggests that environmental factors such as irritation and cutaneous infection play a crucial role in triggering and/or aggravating the disease. Of note, AD skin is susceptible to bacterial, fungal and viral infections, and microorganisms may colonize the skin and aggravate AD symptoms. Overall, understanding the mechanisms by which these risk factors affect the cutaneous immunity of patients with AD is of great importance for developing a precision medicine approach for treatment. This review summarizes recent developments in exogenous factors involved in the pathogenesis of AD, with special emphasis on irritants and microbial infections.

Colonization With Staphylococcus aureus in Atopic Dermatitis Patients: Attempts to Reveal the Unknown

Atopic dermatitis (AD) patients are massively colonized with Staphylococcus aureus (S. aureus) in lesional and non-lesional skin. A skin infection may become systemic if left untreated. Of interest, the incidence of multi-drug resistant S. aureus (MRSA) in AD patients is higher as compared to a healthy population, which makes treatment even more challenging. Information on the specific genetic background of S. aureus accompanying and/or causing AD flares would be of great importance in terms of possible treatment option development. In this review, we summarized the data on the prevalence of S. aureus in general in AD skin, and the prevalence of specific clones that might be associated with flares of eczema. We put our special interest in the presence and role of staphylococcal enterotoxins as important virulence factors in the epidemiology of AD-derived S. aureus. Also, we summarize the present and potentially useful future anti-staphylococcal treatment.

Eczema Herpeticum: Clinical and Pathophysiological Aspects

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease in the world. AD is a complex pathology mainly characterized by an impaired skin barrier, immune response dysfunction, and unbalanced skin microbiota. Moreover, AD patients exhibit an increased risk of developing bacterial and viral infections. One of the most current, and potentially life-threatening, viral infection is caused by herpes simplex virus (HSV), which occurs in about 3% of AD patients under the name of eczema herpeticum (EH). Following a first part dedicated to the clinical features, virological diagnosis, and current treatments of EH, this review will focus on the description of the pathophysiology and, more particularly, the presently known predisposing factors to herpetic complications in AD patients. These factors include those related to impairment of the skin barrier such as deficit in filaggrin and anomalies in tight and adherens junctions. In addition, low production of the antimicrobial peptides cathelicidin LL-37 and human β-defensins; overexpression of cytokines such as interleukin (IL)-4, IL-13, IL-25, IL-33, and thymic stromal lymphopoietin (TSLP); or downregulation of type I to III interferons as well as defect in functions of immune cells such as dendritic, natural killer, and regulatory T cells have been involved. Otherwise, genetic polymorphisms and AD topical calcineurin inhibitor treatments have been associated with an increased risk of EH. Finally, dysbiosis of skin microbiota characterized in AD patients by Staphylococcus aureus colonization and toxin secretion, such as α-toxin, has been described as promoting HSV replication and could therefore contribute to EH.

LL-37-induced caspase-independent apoptosis is associated with plasma membrane permeabilization in human osteoblast-like cells

The host defense peptide LL-37 is active against both gram-positive and gram-negative bacteria, but it has also been shown to reduce human host cell viability. However, the mechanisms behind LL-37-induced human host cell cytotoxicity are not yet fully understood. Here, we assess if LL-37-evoked attenuation of human osteoblast-like MG63 cell viability is associated with apoptosis, and if the underlying mechanism may involve LL-37-induced plasma membrane permeabilization. MG63 cell viability and plasma membrane permeabilization were investigated by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method and by measuring lactate dehydrogenase (LDH) release, respectively. Apoptosis was assessed by the terminal deoxynucleotidyl dUTP nick end labeling (TUNEL) assay and Annexin V flow cytometry, and caspase-3 and poly (ADP-ribose) polymerase (PARP) cleavage were determined by Western blot. LL-37 (4 and 10 μM) reduced both cell number and cell viability, and these effects were associated with a pro-apoptotic effect demonstrated by positive TUNEL staining and Annexin V flow cytometry. LL-37-induced apoptosis was not coupled to either caspase-3 or PARP cleavage, suggesting that LL-37 causes caspase-independent apoptosis in MG63 cells. Both LL-37 and the well-known plasma membrane permeabilizer Triton X-100 reduced cell viability and stimulated LDH release. Triton X-100-treated cells showed positive TUNEL staining, and the detergent accumulated cells in late apoptosis/necrosis. Similar to LL-37, Triton X-100 caused no PARP cleavage. We conclude that LL-37 promotes caspase-independent apoptosis, and that this effect seems coupled to plasma membrane permeabilization in human MG63 cells.

The infectious complications of atopic dermatitis

OBJECTIVE

Atopic dermatitis (AD) is a chronic inflammatory skin disease that is complicated by an increased risk for skin and systemic infections. Preventive therapy for AD is based on skin barrier improvement and anti-inflammatory treatments, whereas overt skin and systemic infections require antibiotics or antiviral treatments. This review updates the pathophysiology, diagnosis, management, controversy of antibiotic use, and potential treatments of infectious complications of AD.

DATA SOURCES

Published literature obtained through PubMed database searches and clinical pictures.

STUDY SELECTIONS

Studies relevant to the mechanisms, diagnosis, management, and potential therapy of infectious complications of AD.

RESULTS

Skin barrier defects, type 2 inflammation, Staphylococcusaureus colonization, and cutaneous dysbiosis are the major predisposing factors for the increased infections in AD. Although overt infections require antibiotics, the use of antibiotics in AD exacerbation remains controversial.

CONCLUSION

Infectious complications are a comorbidity of AD. Although not common, systemic bacterial infections and eczema herpeticum can be life-threatening. Preventive therapy of infections in AD emphasizes skin barrier improvement and anti-inflammatory therapy. The use of antibiotics in AD exacerbation requires further studies.

Cinnamtannin B1 attenuates rosacea-like signs via inhibition of pro-inflammatory cytokine production and down-regulation of the MAPK pathway

Background

Rosacea is a common inflammatory disease of facial skin. Dysregulation of innate immunity with enhanced inflammation and increased abundance of LL-37 at the epidermal site is a characteristic feature of rosacea. Cinnamtannin B1 (CB1) is a condensed tannin with anti-inflammatory and anti-microbial activities. The aims of the study were to evaluate the potential of CB1 as a therapy for rosacea and to characterize the potential mechanisms of action.

Methods

We intraperitoneally administered 20 mg/kg CB1 once daily for 2 days into the LL-37-induced mouse model of rosacea. The effects of CB1 in vivo were evaluated by the observations of lesions, histology, immunohistochemistry, and the transcription and translation of pro-inflammatory cytokines and chemokines. Human keratinocyte HaCaT and monocyte THP-1 were used to characterize the effects of CB1 on LL-37-induced inflammation in vitro. The changes in pro-inflammatory chemokine interleukin-8 (IL-8) were quantitated by enzyme-linked immunosorbent assay (ELISA), and the expressions of genes involved were determined by Western blotting.

Results

CB1 attenuated local redness, inflammation, and neutrophil recruitment in the mouse model of rosacea in vivo. CB1 suppressed myeloperoxidase (MPO) and macrophage inflammatory protein 2 (MIP-2) production, a functional homolog of interleukin-8 (IL-8), at the lesions. In vitro experiments confirmed that CB1 reversed the LL-37-induced IL-8 production in human keratinocytes HaCaT and monocyte THP-1 cells. CB1 inhibited IL-8 production through downregulating the phosphorylation of extracellular signal-regulated kinase (ERK) in the mitogen-activated protein kinase (MAPK) pathway.

Conclusion

CB1 attenuated LL-37-induced inflammation, specifically IL-8 production, through inhibiting the phosphorylation of ERK. CB1 has potential as a treatment for rosacea.

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.

Staphylococcus aureus and Hyper-IgE Syndrome

Hyper-immunoglobulin E syndrome (HIES) is a primary immunodeficiency disease characterized by recurrent Staphylococcus aureus (S. aureus) infections, eczema, skeletal abnormalities and high titers of serum immunoglobulin E. Although the genetic basis of HIES was not known for almost a half century, HIES most frequently exhibits autosomal dominant trait that is transmitted with variable expressivity. Careful genetic studies in recent years identified dominant-negative mutations in human signal transducer and activator of transcription 3 (STAT3) gene as the cause of sporadic and dominant forms of HIES. The STAT3 mutations were localized to DNA-binding, SRC homology 2 (SH2) and transactivating domains and disrupted T helper 17 (T_H17) cell differentiation and downstream expression of T_H17 cytokines IL-17 and IL-22. Deficiency of IL-17 and IL-22 in turn is responsible for suboptimal expression of anti-staphylococcal host factors, such as neutrophil-recruiting chemokines and antimicrobial peptides, by human keratinocytes and bronchial epithelial cells. T_H17 cytokines deficiency thereby explains the recurrent staphylococcal lung and skin infections of HIES patients.

Atopic dermatitis epidemiology and unmet need in the United Kingdom

Atopic dermatitis (AD), also known as atopic eczema, is a chronic inflammatory skin condition associated with a significant health-related and socioeconomic burden, and is characterized by intense itch, disruption of the skin barrier, and upregulation of type 2-mediated immune responses. The United Kingdom (UK) has a high prevalence of AD, affecting 11-20% of children and 5-10% of adults. Approximately 2% of all cases of childhood AD in the UK are severe. Despite this, most AD treatments are performed at home, with little contact with healthcare providers or services. Here, we discuss the course of AD, treatment practices, and unmet need in the UK. Although the underlying etiology of the disease is still emerging, AD is currently attributed to skin barrier dysfunction and altered inflammatory responses. Management of AD focuses on avoiding triggers, improving skin hydration, managing exacerbating factors, and reducing inflammation through topical and systemic immunosuppressants. However, there is a significant unmet need to improve the overall management of AD and help patients gain control of their disease through safe and effective treatments. Approaches that target individual inflammatory pathways (e.g. dupilumab, anti-interleukin (IL)-4 receptor α) are emerging and likely to provide further therapeutic opportunities for patient benefit.

Selective JAK1 Inhibitors for the Treatment of Atopic Dermatitis: Focus on Upadacitinib and Abrocitinib

Atopic dermatitis is a common, chronic, immune-mediated disease associated with several comorbidities. Elevated levels of T helper (Th)2, Th22, and also some Th1 and Th17 cytokines are found in atopic dermatitis skin lesions. Similar to psoriasis, there is a tendency towards increased use of more targeted therapies. However, there are still several unmet needs in the treatment of atopic dermatitis concerning long-term efficacy, tolerability, safety, route of administration, and cost. The increased knowledge of atopic dermatitis pathogenesis and the role of Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathways has allowed the development of new compounds to inhibit this intracellular signaling pathway implicated in atopic dermatitis-related immune responses. Currently, JAK inhibitors are an important focus of therapeutic research for atopic dermatitis. Upadacitinib and abrocitinib are oral small molecules that inhibit the JAK/STAT pathway by selectively blocking JAK1. Data from phase II and III trials are encouraging, revealing that JAK1 inhibitors are effective and well-tolerated agents for moderate-to-severe atopic dermatitis. Selective JAK1 inhibitors may represent an important therapeutic option to be included in the treatment algorithm of atopic dermatitis, owing to oral administration and a favorable safety and tolerability profile. In this article, we review the current evidence on the efficacy and safety of oral selective JAK1 inhibitors for the treatment of atopic dermatitis.

Pathophysiology and Management of Atopic Dermatitis: A Laconic Review

Conclusion:

Atopic Dermatitis (AD) is long-lasting degenerating skin disease with a characteristic phenotype and stereotypically spread skin lesions. The AD results due to a complex interface among genetic factors, host’s surroundings, pharmacological anomalies and immunological factors. In previous decades, researchers had shown marked interest due to increased prevalence in developed countries. In this review, basics along with the advances in pathogenesis and management of AD have been discussed. The immunological factors i.e. Innate Lymphoid Cells, IL-22 and Toll-like receptors have an important role in the pathogenesis. The proactive topical therapy by skincare, topical glucocorticosteroids and calcineurin inhibitors have improved effect in the management of AD. The human monoclonal antibody-based systemic drug (Duplimab) is a considerable advancement in the management of AD. Other monoclonal antibody-based drugs (Lebrikizumab, Tralokinumab, Apremilast and Nemolizumab) are in different phases of clinical trials. A better understanding of genetics and immunoregulatory cascade will lead to the development of efficacious drugs and better management therapy preventing the relapse of flares and improved life quality of AD patients.

Bidirectional association between atopic dermatitis, conjunctivitis, and other ocular surface diseases: A systematic review and meta-analysis

BACKGROUND

Conjunctivitis and several other ocular surface diseases (OSDs) have been linked to atopic dermatitis (AD) and its treatment.

OBJECTIVES

To examine the association between AD, conjunctivitis, and other OSDs.

METHODS

A systematic review and meta-analysis was performed. Two authors independently searched EMBASE, PubMed, SCOPUS, and Web of Science and performed title/abstract and full-text review and data abstraction. Pooled random-effects prevalence and odds ratios (ORs) with 95% confidence intervals (CIs) were estimated.

RESULTS

The search yielded 5719 nonduplicate articles; 134 were included in the quantitative analysis. AD was associated with conjunctivitis compared to reference individuals (OR, 2.78; 95% CI, 2.33-3.32); the prevalences of conjunctivitis in patients with AD and reference individuals were 31.7% (95% CI, 27.7-35.9) and 13.3% (95% CI, 11.0-15.7), respectively. Keratoconus (OR, 3.71; 95% CI, 1.99-6.94) and ocular herpes simplex (OR, 3.65; 95% CI 2.04-6.51) were also associated with AD.

LIMITATIONS

Disease definitions differed and often relied on self-reports. Few studies provided data concerning AD phenotype or OSDs other than conjunctivitis.

CONCLUSIONS

Conjunctivitis is the most common ocular comorbidity in AD. Signs and symptoms of conjunctivitis and other OSDs in AD may be underreported, making proactive inquiry and examination by physicians treating patients with AD important.

Skin Viral Infections: Host Antiviral Innate Immunity and Viral Immune Evasion

The skin is an active immune organ that functions as the first and largest site of defense to the outside environment. Serving as the primary interface between host and pathogen, the skin’s early immune responses to viral invaders often determine the course and severity of infection. We review the current literature pertaining to the mechanisms of cutaneous viral invasion for classical skin-tropic, oncogenic, and vector-borne skin viruses. We discuss the skin’s evolved mechanisms for innate immune viral defense against these invading pathogens, as well as unique strategies utilized by the viruses to escape immune detection. We additionally explore the roles that demographic and environmental factors, such as age, biological sex, and the cutaneous microbiome, play in altering the host immune response to viral threats.

Saline in Dermatology: A literature review

BACKGROUND

Saline, with its different concentrations, is the most used crystalloid solution in medicine. In dermatology, no large studies investigated the benefits of saline. The aim of this article is to review the different possible uses of saline in dermatology, in order to give final recommendations based on the literature review and our experience.

METHODS

We performed a literature search based on PubMed, EMBASE, WHO Global Health Library, Virtual Health Library, Web of Science, Scopus, Google Scholar, and Research gate. using the keywords: saline, physiological, hypertonic, isotonic, hypotonic, salt solution, sodium chloride, 0.9% NaCl, solvent, drug delivery, injection mixtures, diluent, sclerosant, intravenous, intralesional, injection, topical, soaks, fomentation, inhalation, alopecia, psoriasis, scars, atopic dermatitis, eczema, bromoderma, iododerma, lipodystrophy, in various combinations with the Boolean operators AND, OR and NOT. We also hand-searched textbooks.

RESULTS

Saline was used as a diluent with intralesional injection of steroids to minimize the risk of steroid-induced atrophy, being safe and free from preservatives that may precipitate steroids at site of injection and maximize their side effects. Saline has also been used after surgery, when atrophic scars take place or anticipated, and through injection in leishmaniasis, granuloma annulare, atrophic acne scars before using other expensive and less tolerated treatment options.

CONCLUSIONS

The saline represents a helpful option as a diluent with intralesional injection of steroids in various dermatologic therapeutic indications. Moreover, the use of saline in this setting could help to minimize the risk of steroid-induced atrophy. We encourage the use of saline after surgery, when atrophic scars take place or anticipated. Also, we encourage a trial of saline injection in leishmaniasis, granuloma annulare, atrophic acne scars before using other expensive and less tolerated treatment options.

Phosphatidylinositol-specific phospholipase C enhances epidermal penetration by Staphylococcus aureus

Staphylococcus aureus (S. aureus) commonly colonizes the human skin and nostrils. However, it is also associated with a wide variety of diseases. S. aureus is frequently isolated from the skin of patients with atopic dermatitis (AD), and is linked to increased disease severity. S. aureus impairs the skin barrier and triggers inflammation through the secretion of various virulence factors. S. aureus secretes phosphatidylinositol-specific phospholipase C (PI-PLC), which hydrolyses phosphatidylinositol and cleaves glycosylphosphatidylinositol-anchored proteins. However, the role of S. aureus PI-PLC in the pathogenesis of skin diseases, including AD, remains unclear. In this study, we sought to determine the role of S. aureus PI-PLC in the pathogenesis of skin diseases. PI-PLC was observed to enhance the invasion and persistence of S. aureus in keratinocytes. Besides, PI-PLC promoted the penetration of S. aureus through the epidermal barrier in a mouse model of AD and the human organotypic epidermal equivalent. Furthermore, the loss of PI-PLC attenuated epidermal hyperplasia and the infiltration of Gr-1⁺ cells and CD4⁺ cells induced by S. aureus infection in the mouse model of AD. Collectively, these results indicate that PI-PLC eases the entry of S. aureus into the dermis and aggravates acanthosis and immune cell infiltration in infected skin.

The STAPH Score: A Predictor of Staphylococcus aureus as the Causative Microorganism of Native Vertebral Osteomyelitis

Background

Staphylococcus aureus (SA) is the most common causative microorganism in native vertebral osteomyelitis (NVO). Few studies have compared the clinical features of NVO due to SA (SA-NVO) and NVO due to other organisms (NSA-NVO). This study was conducted to validate a predictive score for SA-NVO to facilitate NVO treatment without broad-spectrum antimicrobial agents.

Methods

This retrospective study compared the clinical features of patients with SA-NVO and NSA-NVO who were diagnosed from 2004 to 2019. Univariate associations were assessed using χ ², Fisher's exact, or Mann-Whitney U test. Multivariable analysis was conducted using logistic regression. The optimal age cutoff point was determined by classification and regression tree analysis.

Results

Among 155 NVO patients, 98 (63.2%) had a microbiologically confirmed diagnosis: 40 (25.8%) with SA-NVO and 58 (37.4%) with NSA-NVO. Six predictors, either independently associated with SA-NVO or clinically relevant, were used to develop the STAPH prediction score: atopic dermatitis (Skin) (3 points); recent Trauma (2 points); Age < 67 years (1 point); Abscess (1 point); central venous Port catheter (2 points); and History of puncture (2 points). In a receiver operating characteristic analysis, the area under the curve was 0.84 (95% confidence interval, 0.76-0.91). The best cutoff point was 3. A score ≥3 had a sensitivity, specificity, positive predictive value, and negative predictive value of 58%, 84%, 84%, and 73%, respectively.

Conclusions

The STAPH score has relatively high specificity for use by clinicians to predict SA as the causative microorganism in patients with NVO until results of a confirmatory culture are available.

Cytokinocytes: the diverse contribution of keratinocytes to immune responses in skin

The skin serves as the primary interface between our body and the external environment and acts as a barrier against entry of physical agents, chemicals, and microbes. Keratinocytes make up the main cellular constitute of the outermost layer of the skin, contributing to the formation of the epidermis, and they are crucial for maintaining the integrity of this barrier. Beyond serving as a physical barrier component, keratinocytes actively participate in maintaining tissue homeostasis, shaping, amplifying, and regulating immune responses in skin. Keratinocytes act as sentinels, continuously monitoring changes in the environment, and, through microbial sensing, stretch, or other physical stimuli, can initiate a broad range of inflammatory responses via secretion of various cytokines, chemokines, and growth factors. This diverse function of keratinocytes contributes to the highly variable clinical manifestation of skin immune responses. In this Review, we highlight the highly diverse functions of epidermal keratinocytes and their contribution to various immune-mediated skin diseases.

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.

Smart Titanium Coating Composed of Antibiotic Conjugated Peptides as an Infection-Responsive Antibacterial Agent

Antibacterial coating is rapidly emerging as a pivotal strategy for mitigating spread of bacterial pathogens. However, many challenges still need to be overcome in order to develop a smart coating that can achieve on-demand antibacterial effects. In this study, a Staphylococcus aureus (S. aureus) sensitive peptide sequence is designed, and an antibiotic is then conjugated with this tailor-made peptide. The antibiotic-peptide conjugate is then linked to the surface of a titanium implant, where the peptide can be recognized and cleaved by an enzyme secreted by S. aureus. This allows for the release of antibiotics in the presence of S. aureus, thus achieving delivery of an antibacterial specifically when an infection occurs.

Atopic dermatitis microbiomes stratify into ecologic dermotypes enabling microbial virulence and disease severity

BACKGROUND

Atopic dermatitis (AD) is a common skin disease affecting up to 20% of the global population, with significant clinical heterogeneity and limited information about molecular subtypes and actionable biomarkers. Although alterations in the skin microbiome have been described in subjects with AD during progression to flare state, the prognostic value of baseline microbiome configurations has not been explored.

OBJECTIVE

Our aim was to identify microbial signatures on AD skin that are predictive of disease fate.

METHODS

Nonlesional skin of patients with AD and healthy control subjects were sampled at 2 time points separated by at least 4 weeks. Using whole metagenome analysis of skin microbiomes of patients with AD and control subjects (n = 49 and 189 samples), we identified distinct microbiome configurations (dermotypes A and B). Blood was collected for immunophenotyping, and skin surface samples were analyzed for correlations with natural moisturizing factors and antimicrobial peptides.

RESULTS

Dermotypes were robust and validated across 2 additional cohorts (63 individuals), with strong enrichment of subjects with AD in dermotype B. Dermotype B was characterized by reduced microbial richness, depletion of Cutibacterium acnes, Dermacoccus and Methylobacterium species, individual-specific outlier abundance of Staphylococcus species (eg, S epidermidis, S capitis, S aureus), and enrichment in metabolic pathways (eg, branched chain amino acids and arginine biosynthesis) and virulence genes (eg, β-toxin, δ-toxin) that defined a pathogenic ecology. Skin surface and circulating host biomarkers exhibited a distinct microbial-associated signature that was further reflected in more severe itching, frequent flares, and increased disease severity in patients harboring the dermotype B microbiome.

CONCLUSION

We report distinct clusters of microbial profiles that delineate the role of microbiome configurations in AD heterogeneity, highlight a mechanism for ongoing inflammation, and provide prognostic utility toward microbiome-based disease stratification.

Topical anti-microbial peptide omiganan recovers cutaneous dysbiosis but does not improve clinical symptoms in patients with mild-to-moderate atopic dermatitis in a phase 2 randomized controlled trial

BACKGROUND

Dysbiosis and colonization with Staphylococcus aureus is considered to play an important role in the pathogenesis of atopic dermatitis (AD). Recovering this dysbiosis may improve AD symptoms. Omiganan is a synthetic indolicidin analogue antimicrobial peptide with activity against S. aureus and could be a viable new treatment option for AD.

OBJECTIVE

To explore the tolerability, clinical efficacy and pharmacodynamics of omiganan in mild-to-moderate AD.

METHODS

Eighty patients were randomized to omiganan 1%, 1.75%, 2.5% or vehicle twice daily for 28 days on all lesions. Weekly visits included clinical scores, and microbiological and pharmacodynamic assessments of one 'target lesion'.

RESULTS

In all omiganan treatment groups dysbiosis was recovered by reducing Staphylococcus abundance and increasing diversity. A reduction of cultured S. aureus was observed in all omiganan treatment groups, with a significant reduction for omiganan 2.5% compared to vehicle (-93.5%, 95%CI=-99.2%/-28.5% p=0.02). No significant clinical improvement was observed.

CONCLUSION

Topical administration of omiganan twice daily for up to 28 days in patients with mild-to-moderate AD led to a recovery of dysbiosis, but without clinical improvement. Therefore, a mono-treatment that selectively targets the microbiome does not appear to be a successful treatment strategy in mild-to-moderate AD.

Antimicrobial Peptide Exposure Selects for Resistant and Fit Stenotrophomonas maltophilia Mutants That Show Cross-Resistance to Antibiotics

Antimicrobial peptides (AMPs) are essential components of the innate immune system and have been proposed as promising therapeutic agents against drug-resistant microbes. AMPs possess a rapid bactericidal mode of action and can interact with different targets, but bacteria can also avoid their effect through a variety of resistance mechanisms. Apart from hampering treatment by the AMP itself, or that by other antibiotics in the case of cross-resistance, AMP resistance might also confer cross-resistance to innate human peptides and impair the anti-infective capability of the human host. A better understanding of how resistance to AMPs is acquired and the genetic mechanisms involved is needed before using these compounds as therapeutic agents. Using experimental evolution and whole-genome sequencing, we determined the genetic causes and the effect of acquired de novo resistance to three different AMPs in the opportunistic pathogen Stenotrophomonas maltophilia, a bacterium that is intrinsically resistant to a wide range of antibiotics. Our results show that AMP exposure selects for high-level resistance, generally without any reduction in bacterial fitness, conferred by mutations in different genes encoding enzymes, transporters, transcriptional regulators, and other functions. Cross-resistance to AMPs and to other antibiotic classes not used for selection, as well as collateral sensitivity, was observed for many of the evolved populations. The relative ease by which high-level AMP resistance is acquired, combined with the occurrence of cross-resistance to conventional antibiotics and the maintained bacterial fitness of the analyzed mutants, highlights the need for careful studies of S. maltophilia resistance evolution to clinically valuable AMPs.IMPORTANCE Stenotrophomonas maltophilia is an increasingly relevant multidrug-resistant (MDR) bacterium found, for example, in people with cystic fibrosis and associated with other respiratory infections and underlying pathologies. The infections caused by this nosocomial pathogen are difficult to treat due to the intrinsic resistance of this bacterium against a broad number of antibiotics. Therefore, new treatment options are needed, and considering the growing interest in using AMPs as alternative therapeutic compounds and the restricted number of antibiotics active against S. maltophilia, we addressed the potential for development of AMP resistance, the genetic mechanisms involved, and the physiological effects that acquisition of AMP resistance has on this opportunistic pathogen.

Amelioration of Compound 48/80-Mediated Itch and LL-37-Induced Inflammation by a Single-Stranded Oligonucleotide

Numerous inflammatory skin disorders display a high prevalence of itch. The Mas-related G protein coupled receptor X2 (MRGPRX2) has been shown to modulate itch by inducing non-IgE-mediated mast cell degranulation and the release of endogenous inducers of pruritus. Various substances collectively known as basic secretagogues, which include inflammatory peptides and certain drugs, can trigger MRGPRX2 and thereby induce pseudo-allergic reactions characterized by histamine and protease release as well as inflammation. Here, we investigated the capacity of an immunomodulatory single-stranded oligonucleotide (ssON) to modulate IgE-independent mast cell degranulation and, more specifically, its ability to inhibit the basic secretagogues compound 48/80 (C48/80)-and LL-37 in vitro and in vivo. We examined the effect of ssON on MRGPRX2 activation in vitro by measuring degranulation in a human mast cell line (LAD2) and calcium influx in MRGPRX2-transfected HEK293 cells. To determine the effect of ssON on itch, we performed behavioral studies in established mouse models and collected skin biopsies for histological analysis. Additionally, with the use of a rosacea mouse model and RT-qPCR, we investigated the effect on ssON on LL-37-induced inflammation. We reveal that both mast cell degranulation and calcium influx in MRGPRX2 transfected HEK293 cells, induced by the antimicrobial peptide LL-37 and the basic secretagogue C48/80, are effectively inhibited by ssON in a dose-dependent manner. Further, ssON demonstrates a capability to inhibit LL-37 and C48/80 activation in vivo in two mouse models. We show that intradermal injection of ssON in mice is able to block itch induced via C48/80 in a dose-dependent manner. Histological staining revealed that ssON inhibits acute mast cell degranulation in murine skin treated with C48/80. Lastly, we show that ssON treatment ameliorates LL-37-induced inflammation in a rosacea mouse model. Since there is a need for new therapeutics targeting non-IgE-mediated activation of mast cells, ssON could be used as a prospective drug candidate to resolve itch and inflammation in certain dermatoses.

Targeting IL-4 for the Treatment of Atopic Dermatitis

Atopic dermatitis (AD) is an immune-mediated inflammatory skin disease characterized by a predominant type 2 immune response. Type 2 immunity is driven by multiple cytokines, including interleukin (IL)‑4 and IL-13 that are considered central to AD pathogenesis and key therapeutic targets. The dual inhibition of these two cytokines or the selective inhibition of IL-13 proved elevated efficacy in treating AD, whereas the selective inhibition of IL-4 has been poorly investigated as IL-4 inhibiting agents did not show any advance in clinical development programs. This review describes the pathogenic role of IL-4 in AD and briefly resumes the main features of compounds selectively blocking IL-4.

Selection of antimicrobial frog peptides and temporin-1DRa analogues for treatment of bacterial infections based on their cytotoxicity and differential activity against pathogens

Cationic, amphipathic, α-helical host-defense peptides (HDPs) that are naturally secreted by certain species of frogs (Anura) possess potent broad-spectrum antimicrobial activity and show therapeutic potential as alternatives to treat infections by multidrug-resistant pathogens. Fourteen amphibian skin peptides and twelve analogues of temporin-1DRa were studied for their antimicrobial activities against clinically relevant human or animal skin infection-associated pathogens. For comparison, antimicrobial potencies of frog skin peptides against a range of probiotic lactobacilli were determined. We used the VITEK 2 system to define a profile of antibiotic susceptibility for the bacterial panel. The minimal inhibitory concentration (MIC) values of the naturally occurring temporin-1DRa, CPF-AM1, alyteserin-1c, hymenochirin-2B, and hymenochirin-4B for pathogenic bacteria were threefold to ninefold lower than the values for the tested probiotic strains. Similarly, temporin-1DRa and its [Lys⁴ ], [Lys⁵ ], and [Aib⁸ ] analogues showed fivefold to 6.5-fold greater potency against the pathogens. In the case of PGLa-AM1, XT-7, temporin-1DRa and its [D-Lys⁸ ] and [Aib¹³ ] analogues, no apoptosis or necrosis was detected in human peripheral blood mononuclear cells at concentrations below or above the MIC. Given the differential activity against commensal bacteria and pathogens, some of these peptides are promising candidates for further development into therapeutics for topical treatment of skin infections.

Development of a vaccine against Staphylococcus aureus invasive infections: Evidence based on human immunity, genetics and bacterial evasion mechanisms

Invasive Staphylococcus aureus infections are a leading cause of morbidity and mortality in both hospital and community settings, especially with the widespread emergence of virulent and multi-drug resistant methicillin-resistant S. aureus strains. There is an urgent and unmet clinical need for non-antibiotic immune-based approaches to treat these infections as the increasing antibiotic resistance is creating a serious threat to public health. However, all vaccination attempts aimed at preventing S. aureus invasive infections have failed in human trials, especially all vaccines aimed at generating high titers of opsonic antibodies against S. aureus surface antigens to facilitate antibody-mediated bacterial clearance. In this review, we summarize the data from humans regarding the immune responses that protect against invasive S. aureus infections as well as host genetic factors and bacterial evasion mechanisms, which are important to consider for the future development of effective and successful vaccines and immunotherapies against invasive S. aureus infections in humans. The evidence presented form the basis for a hypothesis that staphylococcal toxins (including superantigens and pore-forming toxins) are important virulence factors, and targeting the neutralization of these toxins are more likely to provide a therapeutic benefit in contrast to prior vaccine attempts to generate antibodies to facilitate opsonophagocytosis.

Psoriasis and Antimicrobial Peptides

Psoriasis is a systemic inflammatory disease caused by crosstalk between various cells such as T cells, neutrophils, dendritic cells, and keratinocytes. Antimicrobial peptides (AMPs) such as β-defensin, S100, and cathelicidin are secreted from these cells and activate the innate immune system through various mechanisms to induce inflammation, thus participating in the pathogenesis of psoriasis. In particular, these antimicrobial peptides enhance the binding of damage-associated molecular patterns such as self-DNA and self-RNA to their receptors and promote the secretion of interferon from activated plasmacytoid dendritic cells and keratinocytes to promote inflammation in psoriasis. Neutrophil extracellular traps (NETs), complexes of self-DNA and proteins including LL-37 released from neutrophils in psoriatic skin, induce Th17. Activated myeloid dendritic cells secrete a mass of inflammatory cytokines such as IL-12 and IL-23 in psoriasis, which is indispensable for the proliferation and survival of T cells that produce IL-17. AMPs enhance the production of some of Th17 and Th1 cytokines and modulate receptors and cellular signaling in psoriasis. Inflammation induced by DAMPs, including self-DNA and RNA released due to microinjuries or scratches, and the enhanced recognition of DAMPs by AMPs, may be involved in the mechanism underlying the Köbner phenomenon in psoriasis.

Which Way Do We Go? Complex Interactions in Atopic Dermatitis Pathogenesis

Atopic dermatitis (AD) is a common, chronic, inflammatory skin condition characterized by recurrent and pruritic skin eruptions. Multiple factors contribute to the pathogenesis of AD, including skin barrier dysfunction, microbial dysbiosis, and immune dysregulation. Interactions among these factors form a complex, multidirectional network that can reinforce atopic skin disease but can also be ameliorated by targeted therapies. This review summarizes the complex interactions among contributing factors in AD and the implications on disease development and therapeutic interventions.

Dupilumab therapy for patients with refractory eosinophilic otitis media associated with bronchial asthma

OBJECTIVES

Eosinophilic otitis media (EOM) is an intractable otitis media mostly associated with bronchial asthma. Dupilumab, an anti-interleukin (IL)-4 receptor (R)α, is effective and has been approved for use in patients with moderate to severe bronchial asthma, atopic dermatitis and chronic rhinosinusitis with nasal polyposis, whose diseases are not controlled by previous treatments including other molecular targeted drugs. We aimed to assess efficacy of dupilumab in three EOM patients with associated bronchial asthma, who were poor responders to previous topical and systemic corticosteroid therapy and molecular targeted therapies.

PATIENTS AND METHODS

Three patients with severe, refractory EOM (two with a granulation type) associated with bronchial asthma received dupilumab as add-on therapy for at least 6 months. The efficacy of dupilumab therapy was evaluated using severity scores, symptom scores, hearing acuities, temporal bone computed tomography (CT) scores, and surrogate markers before and after therapy.

RESULTS

Severity scores in all patients were dramatically reduced to 2 points or less (full score: 16 points) after initiation of therapy. Air conduction hearing levels were improved in all patients. Temporal bone CT scores in two patients were reduced, and serum IgE levels in all three patients also decreased following therapy.

CONCLUSION

We provide the first report that add-on dupilumab therapy was effective in patients with severe, refractory EOM who did not respond to the treatments including other molecular targeted therapy. Patients with severe middle ear mucosal change may benefit particularly from dupilumab therapy.

The Antimicrobial Cathelicidin CRAMP Augments Platelet Activation during Psoriasis in Mice

Platelet-associated complications including thrombosis, thrombocytopenia, and haemorrhage are commonly observed during various inflammatory diseases such as psoriasis. Although several mechanisms that may contribute to the dysfunction of platelets during inflammatory diseases have been reported, knowledge on the primary molecules/mechanisms that underpin platelet-associated complications in such conditions is not fully established. Here, we report the significance of the mouse antimicrobial cathelicidin, mouse cathelicidin-related antimicrobial peptide (mCRAMP) (an orthologue of LL37 in humans), on the modulation of platelet reactivity during psoriasis using Imiquimod-induced psoriasis in mice as an inflammatory disease model for psoriasis vulgaris in humans. The activation of platelets during psoriasis is increased as evidenced by the elevated levels of fibrinogen binding and P-selectin exposure on the surface of platelets, and the level of soluble P-selectin in the plasma of psoriatic mice. The skin and plasma of psoriatic mice displayed increased levels of mCRAMP. Moreover, the plasma of psoriatic mice augmented the activation of platelets obtained from healthy mice. The effect of mCRAMP is partially mediated through formyl peptide receptor 2/3 (Fpr2/3, the orthologue to human FPR2/ALX) in platelets as a significant reduction in their activation was observed when FPR2/ALX-selective inhibitors such as WRW₄ or Fpr2/3-deficient mouse platelets were used in these assays. Since the level of antimicrobial cathelicidin is increased in numerous inflammatory diseases such as psoriasis, atherosclerosis, and inflammatory bowel disease, the results of this study point towards a critical role for antimicrobial cathelicidin and FPR2/ALX in the development of platelet-related complications in such diseases.

The Dual Role of Antimicrobial Peptides in Autoimmunity

Autoimmune diseases (AiDs) are characterized by the destruction of host tissues by the host immune system. The etiology of AiDs is complex, with the implication of multiple genetic defects and various environmental factors (pathogens, antibiotic use, pollutants, stress, and diet). The interaction between these two compartments results in the rupture of tolerance against self-antigens and the unwanted activation of the immune system. Thanks to animal models, the immunopathology of many AiDs is well described, with the implication of both the innate and adaptive immune systems. This progress toward the understanding of AiDs led to several therapies tested in patients. However, the results from these clinical trials have not been satisfactory, from reversing the course of AiDs to preventing them. The need for a cure has prompted many investigators to explore alternative aspects in the immunopathology of these diseases. Among these new aspects, the role of antimicrobial host defense peptides (AMPs) is growing. Indeed, beyond their antimicrobial activity, AMPs are potent immunomodulatory molecules and consequently are implicated in the development of numerous AiDs. Importantly, according to the disease considered, AMPs appear to play a dual role in autoimmunity with either anti- or pro-inflammatory abilities. Here, we aimed to summarize the current knowledge about the role of AMPs in the development of AiDs and attempt to provide some hypotheses explaining their dual role. Definitely, a complete understanding of this aspect is mandatory before the design of AMP-based therapies against AiDs.