Antimicrobial peptides human beta-defensins and cathelicidin LL-37 induce the secretion of a pruritogenic cytokine IL-31 by human mast cells

Interleukin-31, Interleukin-31RA, and OSMR Expression Levels in Post-burn Hypertrophic Scars

BACKGROUND

Although several studies have shown the role of interleukin-31 (IL-31) and its receptors in inducing pruritus in certain skin disorders, knowledge of its role in post-burn hypertrophic scars is insufficient. Therefore, the histopathological expression levels of IL-31, IL-31 receptor alpha (IL-31RA), and oncostatin M receptor (OSMR) in post-burn hypertrophic scar tissues were investigated and compared with normal tissue expression levels.

METHODS

Samples of hypertrophic scar tissue were obtained from 20 burn patients through punch biopsy. Normal samples were obtained from areas adjacent to the burn injury site of the same patients. Samples were placed in 10% neutral buffered formalin, embedded in paraplast, and processed into serial 5-μm sections. Immunohistochemistry results were semi-quantitatively evaluated for IL-31, IL-31RA, and OSMR. By hematoxylin and eosin staining, epidermal and dermal thickness were assessed with a microscope and digital camera. Intensities were rated on a scale of 1 to 4.

RESULTS

Percentages for IL-31, IL-31RA, and OSMR in the epidermal basal layer cell cytoplasm were significantly greater in the burn scar tissue compared to normal skin, as well as the dermal and epidermal thickness (p < .05). There was a significant difference in IL-31 epidermal basal layer intensity in burn scar tissue compared to normal skin (p < .05). Besides the OSMR basal layer intensity, IL-31 and IL-31RA intensities between the burn scar and normal tissues were not significant. However, correlations were significant, indicating that the greater the infiltration percentage, the higher the intensity (p < .05).

CONCLUSIONS

IL-31, IL-31RA, and OSMR expression levels are increased in hypertrophic scars compared with normal tissue.

The RLR/NLR expression and pro-inflammatory activity of tissue mast cells are regulated by cathelicidin LL-37 and defensin hBD-2

Considering the significance of mast cells (MCs) in the course of various physiological and pathological processes, and the pivotal role of endogenous molecules, i.e., cathelicidins and defensins as multifunctional modulators, the study examines the constitutive and cathelicidin LL-37/defensin hBD-2-induced expression of certain NLRs and RLRs, i.e., NOD1, NOD2, and RIG-I, in fully-mature tissue MCs, and the impact of LL-37 and hBD-2 on MC pro-inflammatory activity. All experiments were carried out in vitro on freshly-isolated peritoneal (P)MCs. qRT-PCR, western blotting, flow cytometry, and confocal microscopy were used to evaluate both constitutive and LL-37/hBD-2-induced expression of NOD1, NOD2, and RIG-I receptors. ROS was determined using H2DCFDA, and Boyden microchamber assay was used to define the migratory response. Standard techniques assessed histamine, cysLT, and chemokine generation. PMCs express NOD1, NOD2, and RIG-I constitutively. LL-37 and hBD-2 enhance the expression and induce translocation of the studied receptors and directly activate the pro-inflammatory and migratory responses of PMCs. Observations demonstrate that LL-37 and hBD-2 might augment MC capability and sensitivity to NLR and RLR ligands and strengthen the role of MCs in inflammation.

No difference in human mast cells derived from peanut allergic versus non-allergic subjects

INTRODUCTION

Mast cells are the primary effector cells of allergy. This study aimed at characterizing human peripheral blood-derived mast cells (PBdMC) from peanut allergic and non-allergic subjects by investigating whether the molecular and stimulus-response profile of PBdMC discriminate between peanut allergic and healthy individuals.

METHODS

PBdMC were generated from eight peanut allergic and 10 non-allergic subjects. The molecular profile (cell surface receptor expression) was assessed using flow cytometry. The stimulus-response profile (histamine release induced by secretagogues, secretion of cytokines/chemokines and changes in miRNA expression following anti-IgE activation) was carried out with histamine release test, luminex multiplex assay and miRNA arrays.

RESULTS

Expression of activating receptors (FcϵRI, CD48, CD88, CD117, and C3aR) on PBdMC was not different among peanut allergic and non-allergic subjects. Likewise, inhibitory receptors (CD32, CD200R, CD300a, and siglec-8) displayed comparable levels of expression. Both groups of PBdMC were unresponsive to substance P, compound 48/80 and C5a but released comparable levels of histamine when stimulated with anti-IgE and C3a. Interestingly, among the secreted cytokines/chemokines (IL-8, IL-10, IL-13, IL-23, IL-31, IL-37, MCP-1, VEGF, GM-CSF) PBdMC from peanut allergic subjects showed a different secretion pattern of IL-31 compared to non-allergic subjects. Investigating miRNA expression from resting or activated PBdMC revealed no significantly difference between peanut allergic and non-allergic subjects.

CONCLUSION

The molecular and stimulus-response profile revealed that PBdMC from peanut allergic subjects differently express IL-31 compared to non-allergic subjects. However, since only one altered parameter was found among 893 investigated, it is still questionable if the pathophysiological mechanisms of peanut allergy are revealed in PBdMC.

Chinese Society of Allergy Guidelines for Diagnosis and Treatment of Allergic Rhinitis

Allergic rhinitis (AR) is a global health problem that causes major illnesses and disabilities worldwide. Epidemiologic studies have demonstrated that the prevalence of AR has increased progressively over the last few decades in more developed countries and currently affects up to 40% of the population worldwide. Likewise, a rising trend of AR has also been observed over the last 2-3 decades in developing countries including China, with the prevalence of AR varying widely in these countries. A survey of self-reported AR over a 6-year period in the general Chinese adult population reported that the standardized prevalence of adult AR increased from 11.1% in 2005 to 17.6% in 2011. An increasing number of Journal Articles and imporclinical trials on the epidemiology, pathophysiologic mechanisms, diagnosis, management and comorbidities of AR in Chinese subjects have been published in international peer-reviewed journals over the past 2 decades, and substantially added to our understanding of this disease as a global problem. Although guidelines for the diagnosis and treatment of AR in Chinese subjects have also been published, they have not been translated into English and therefore not generally accessible for reference to non-Chinese speaking international medical communities. Moreover, methods for the diagnosis and treatment of AR in China have not been standardized entirely and some patients are still treated according to regional preferences. Thus, the present guidelines have been developed by the Chinese Society of Allergy to be accessible to both national and international medical communities involved in the management of AR patients. These guidelines have been prepared in line with existing international guidelines to provide evidence-based recommendations for the diagnosis and management of AR in China.

IL-31 is crucial for induction of pruritus, but not inflammation, in contact hypersensitivity

IL-31, which is a member of the IL-6 family of cytokines, is produced mainly by activated CD4⁺ T cells, in particular activated Th2 cells, suggesting a contribution to development of type-2 immune responses. IL-31 was reported to be increased in specimens from patients with atopic dermatitis, and IL-31-transgenic mice develop atopic dermatitis-like skin inflammation, which is involved in the pathogenesis of atopic dermatitis. However, the role of IL-31 in development of contact dermatitis/contact hypersensitivity (CHS), which is mediated by hapten-specific T cells, including Th2 cells, is not fully understood. Therefore, we investigated this using IL-31-deficient (Il31^−/−) mice, which we newly generated. We demonstrated that the mice showed normal migration and maturation of skin dendritic cells and induction of hapten-specific T cells in the sensitization phase of FITC-induced CHS, and normal induction of local inflammation in the elicitation phase of FITC- and DNFB-induced CHS. On the other hand, those mice showed reduced scratching frequency and duration during FITC- and/or DNFB-induced CHS. Our findings suggest that IL-31 is responsible for pruritus, but not induction of local skin inflammation, during CHS induced by FITC and DNFB.

Innate defense regulator IDR-1018 activates human mast cells through G protein-, phospholipase C-, MAPK- and NF-ĸB-sensitive pathways

Host defense (antimicrobial) peptides not only display antimicrobial activities against numerous pathogens but also exert a broader spectrum of immune-modulating functions. Innate defense regulators (IDRs) are a class of host defense peptides synthetically developed from natural or endogenous cationic host defense peptides. Of the IDRs developed to date, IDR-1018 is more efficient not only in killing bacteria but also in regulating the various functions of macrophages and neutrophils and accelerating the wound healing process. Because mast cells intimately participate in wound healing and a number of host defense peptides involved in wound healing are also known to activate mast cells, this study aimed to investigate the effects of IDR-1018 on mast cell activation. Here, we showed that IDR-1018 induced the degranulation of LAD2 human mast cells and caused their production of leukotrienes, prostaglandins and various cytokines and chemokines, including granulocyte-macrophage colony-stimulating factor, interleukin-8, monocyte chemoattractant protein-1 and -3, macrophage-inflammatory protein-1α and -1β, and tumor necrosis factor-α. Furthermore, IDR-1018 increased intracellular calcium mobilization and induced mast cell chemotaxis. The mast cell activation was markedly suppressed by pertussis toxin, U-73122, U0126, SB203580, JNK inhibitor II, and NF-κB activation inhibitor II, suggesting the involvement of G-protein, phospholipase C, ERK, p38, JNK and NF-κB pathways, respectively, in IDR-1018-induced mast cell activation. Notably, we confirmed that IDR-1018 caused the phosphorylation of MAPKs and IκB. Altogether, the current study suggests a novel immunomodulatory role of IDR-1018 through its ability to recruit and activate human mast cells at the sites of inflammation and wounds.

HIGHLIGHTS

We report that IDR-1018 stimulates various functions of human mast cells. IDR-1018-induced mast cell activation is mediated through G protein, PLC, MAPK and NF-κB pathways. IDR-1018 will be a useful therapeutic agent for wound healing.

Interleukin 33 and interleukin 4 regulate interleukin 31 gene expression and secretion from human laboratory of allergic diseases 2 mast cells stimulated by substance P and/or immunoglobulin E

BACKGROUND

Cytokine interleukin (IL) 31 has emerged as an important component of allergic and inflammatory diseases associated with pruritus, such as atopic dermatitis (AD) and mastocytosis. Mast cells (MC) are stimulated by allergic and nonallergic triggers, and play a critical role in such diseases by secreting histamine and tryptase as well as cytokines and chemokines. IL-33 has been reported to augment MC responses, but its effect on secretion of IL-31 is not known.

OBJECTIVES

To investigate whether IL-33 can stimulate the secretion of IL-31 from cultured human MCs and whether this response is augmented by either the neuropeptide substance P (SP) or immunoglobulin E (IgE) and anti-IgE in the absence or presence of IL-4.

METHODS

Laboratory of Allergic Diseases (LAD2) human MCs were cultured in StemProH-34 SFM medium supplemented by stem cell factor and were stimulated either with IL-33 (10 ng /mL) or SP (2 μM), or preincubated with IgE (1 μg/mL) overnight, and then stimulated with anti-IgE (1 μg/mL) for 24 hours. IL-31 gene expression was measured by quantitative polymerase chain reaction, and protein was measured by enzyme-linked immunosorbent assay.

RESULTS

IL-33 (10 ng/mL) induces IL-31 gene expression, synthesis, and secretion from LAD2 cells in the absence of degranulation, whereas SP and IgE on their own have no effect. However, the effect of IL-33 is augmented by SP (2 μM) and/or IgE and anti-IgE (1 μg/mL both) and especially their combination. Moreover, this response is significantly further increased when LAD2 cells are cultured in the presence of IL-4.

CONCLUSION

These findings provide evidence that IL-33 induced secretion of IL-31 from LAD2 MC, an action augmented by novel neuroimmune interactions that may help in the development of new treatments of allergic and inflammatory diseases, especially AD and mastocytosis.

Cathelicidin LL-37 Affects Surface and Intracellular Toll-Like Receptor Expression in Tissue Mast Cells

Undoubtedly, mast cells take part in host defense against microorganisms as they are numerous at the portal of infection, they release many proinflammatory and antimicrobial mediators, and they express pattern recognition receptors, such as TLRs. These receptors play a key role in recognition and binding molecules associated with microorganisms and molecules associated with damage. Cathelicidins exhibit direct antimicrobial activities against a broad spectrum of microbes by perturbing their cell membranes. Accumulating evidence suggests a role for these molecules in supporting cell activation. We examined the impact of human cathelicidin LL-37 on tissue mast cell TLR expression and distribution. Depending on context, we show that LL-37 stimulation resulted in minor to major effects on TLR2, TLR3, TLR4, TLR5, TLR7, and TLR9 expression. Confocal microscopy analysis showed that, upon stimulation, TLRs may translocate from the cell interior to the surface and conversely. FPR2 and EGFR inhibitors reduced the increase in expression of selected receptors. We also established that LL-37 acts as a powerful inducer of CCL3 and ROS generation. These results showed that in response to LL-37, mast cells enhance the capability to detect invading pathogens by modulation of TLR expression in what may be involved FPR2 or EGFR molecules.

JAK/STAT inhibitors and other small molecule cytokine antagonists for the treatment of allergic disease

OBJECTIVE

To provide an overview of janus kinase (JAK), chemoattractant receptor homologous molecule expressed on T_H2 cells (CRTH2), and phosphodiesterase 4 (PDE4) inhibitors in allergic disorders.

DATA SOURCES

PubMed literature review.

STUDY SELECTIONS

Articles included in this review discuss the emerging mechanism of action of small molecule inhibitors and their use in the treatment of atopic dermatitis (AD), asthma, and allergic rhinitis (AR).

RESULTS

Allergic diseases represent a spectrum of diseases, including AD, asthma, and AR. For decades, these diseases have been primarily characterized by increased T_H2 signaling and downstream inflammation. In recent years, additional research has identified disease phenotypes and subsets of patients with non-Th2 mediated inflammation. The increasing heterogeneity of disease has prompted investigators to move away from wide-ranging treatment approaches with immunosuppressive agents, such as corticosteroids, to consider more targeted immunomodulatory approaches focused on specific pathways. In the past decade, inhibitors that target JAK signaling, PDE4, and CRTH2 have been explored for their potential activity in models of allergic disease and therapeutic benefit in clinical trials. Interestingly, although JAK inhibitors provide an opportunity to interfere with cytokine signaling and could be beneficial in a broad range of allergic diseases, current clinical trials are focused on the treatment of AD. Conversely, both PDE4 and CRTH2 inhibitors have been evaluated in a spectrum of allergic diseases. This review summarizes the varying degrees of success that these small molecules have demonstrated across allergic diseases.

CONCLUSION

Emerging therapies currently in development may provide more consistent benefit to patients with allergic diseases by specifically targeting inflammatory pathways important for disease pathogenesis.

[Neurophysiology of atopic pruritus]

Pruritus is one of the major symptoms of inflammatory skin diseases and strongly affects the quality of life in patients. Although the perception of pruritus and pain are closely intertwined, pruritus represents a distinct sensation, which is also significantly different to pain at a neurophysiological level. The pathophysiological basis of chronic and acute pruritus is not fully understood. Besides histamine, a plethora of different neuromediators of itch, including neurotrophins, neuropeptides and their corresponding receptors, have been identified. In atopic dermatitis the release of these mediators leads to an activation of immune cells, such as mast cells and eosinophilic granulocytes, which in turn release neuromediators and cytokines that activate peripheral neurons. This review focuses on the neurophysiological interactions which regulate pruritus and summarizes the function of neurological and inflammatory mediators in atopic pruritus.

IL-31: A new key player in dermatology and beyond

IL-31 is a novel cytokine expressed in many human tissues and involved mainly in T_H2-weighted inflammation. IL-31 signals through a receptor complex consisting of IL-31 receptor α and oncostatin M receptor β. The available data show that IL-31 is strongly linked with chronic pruritic skin disorders, such as atopic eczema, and represents a novel target for directed drug therapy. Regulation of immune responses and cellular differentiation and proliferation are recently elucidated effects of IL-31, suggesting a more complex and diverse area of effect for this novel cytokine. This review summarizes the current knowledge on IL-31 and its receptors and the involvement of IL-31 in diseases both in human subjects and mouse models.

Emerging role of interleukin-31 and interleukin-31 receptor in pruritus in atopic dermatitis

Atopic dermatitis (AD) is a chronic or chronically relapsing, eczematous, severely pruritic skin disorder associated with skin barrier dysfunction. The lesional skin of AD exhibits T helper 2 (T_H 2)-deviated immune reactions. Interleukin-31 (IL-31), preferentially produced from T_H 2 cells, is a potent pruritogenic cytokine, and its systemic and local administration induces scratching behavior in rodents, dogs and monkeys. Recent clinical trials have revealed that administration of an anti-IL-31 receptor antibody significantly alleviates pruritus in patients with AD. In this review, we summarize recent topics related to IL-31 and its receptor with special references to atopic itch.

The antimicrobial peptide, human β-defensin-1, potentiates in vitro osteoclastogenesis via activation of the p44/42 mitogen-activated protein kinases

Previous studies have demonstrated increased expression and raised levels of human β-defensin (hBD)-1 in gingival tissue and crevicular fluid of patients with chronic periodontitis and peri-implantitis, oral bone-resorbing diseases caused by enhanced osteoclastogenesis. Therefore, we aimed to investigate the effect of hBD-1 on osteoclast formation and function and to elucidate the involved signaling pathway in vitro. Human peripheral blood mononuclear cells (PBMCs) were first incubated with various doses of hBD-1 and cell viability was assayed by MTT. PBMCs were treated with macrophage-colony stimulating factor and receptor activator of nuclear factor kappa-B ligand (RANKL) in the presence or absence of non-toxic doses of hBD-1. In vitro osteoclastogenesis was analyzed by tartrate-resistant acid phosphatase (TRAP) staining, osteoclast-specific gene expression, and a resorption pit assay. Involvement of mitogen-activated protein kinases (MAPKs) was studied by immunoblotting and specific MAPK inhibitors. HBD-1 potentiated induction of in vitro osteoclastogenesis by RANKL, as shown by significantly increased number of TRAP-positive multinuclear cells and resorption areas on the dentin slices, and further up-regulated expressions of osteoclast-specific genes compared to those by RANKL treatment (p <0.05). However, hBD-1 treatment without RANKL failed to induce formation of osteoclast-like cells. A significant and further increase in transient phosphorylation of the p44/42 MAPKs was demonstrated by hBD-1 co-treatment (p<0.05), consistent with the inhibitory effect by pretreatment with U0126 or PD98059 on hBD-1-enhanced osteoclastogenesis. Collectively, hBD-1 potentiates the induction of in vitro osteoclastogenesis by RANKL via enhanced phosphorylation of the p44/42 MAPKs.

Emerging Roles for MAS-Related G Protein-Coupled Receptor-X2 in Host Defense Peptide, Opioid, and Neuropeptide-Mediated Inflammatory Reactions

Mast cells (MCs) are tissue-resident immune cells that contribute to host defense but are best known for their roles in allergic and inflammatory diseases. In humans, MCs are divided into two subtypes based on the protease content of their secretory granules. Thus, human lung MCs contain only tryptase and are known as MC_T, whereas skin MCs contain both tryptase and chymase and are known as MC_TC. Patients with severe asthma display elevated MCs in the lung, which undergo phenotypic change from MC_T to MC_TC. Although the human genome contains four Mas related G protein coupled receptor X (MRGPRX) genes, an important feature of MC_TC is that they selectively express MRGPRX2. It is activated by antimicrobial host defense peptides such as human β-defensins and the cathelicidin LL-37 and likely contributes to host defense. MRGPRX2 is also a receptor for the neuropeptide substance P, major basic protein, eosinophil peroxidase, opioids, and many FDA-approved cationic drugs. Increased expression of MRGPRX2 or enhanced downstream signaling likely contributes to chronic inflammatory diseases such as rosacea, atopic dermatitis, chronic urticaria, and severe asthma. In this chapter, I will discuss the expression profile and function of MRGPRX1-4 and review the emerging roles of MRGPRX2 on host defense, chronic inflammatory diseases, and drug-induced pseudoallergic reactions. I will also examine the novel aspects of MRGPRX2 signaling in MCs as it related to degranulation and review the mechanisms of its regulation.

LL-37-induced human mast cell activation through G protein-coupled receptor MrgX2

Human LL-37 is an important class of cationic antimicrobial peptide (CAP) that is known to stimulate mast cell activation. While many studies have been conducted on LL-37, to date little is known about the functional receptors for LL-37-induced human mast cell activation, in particular in terms of the release of de novo synthesized mediators. Thus, the aim of the present study is to identify the functional receptors for LL-37-induced human mast cell activation in terms of the degranulation and release of de novo synthesized mediators and investigate the downstream signalling pathways involved in mast cell activation. Overall, our study importantly demonstrates that LL-37-induced human mast cell degranulation and release of de novo synthesized mediators function primarily through the activation of MrgX2. We furthermore show that LL-37-induced human mast cell line LAD2 cells are involved in the degranulation and release of IL-8, and that FPRL1 and P2X7 have only a partial effect on IL-8 release, and no effect on mast cell degranulation triggered by LL-37. Instead, we find that silencing the expression of MrgX2 in human mast cell significantly inhibits the LL-37-induced degranulation and release of IL-8. Overall, this effect is associated with the activation of the G_i protein, PLC/PKC/Calcium/NFAT, PI3K/Akt and MAPKs signalling pathways.

Friends or Foes? Host defense (antimicrobial) peptides and proteins in human skin diseases

Host defense peptides/proteins (HDPs), also known as antimicrobial peptides/proteins (AMPs), are key molecules in the cutaneous innate immune system. AMPs/HDPs historically exhibit broad-spectrum killing activity against bacteria, enveloped viruses, fungi and several parasites. Recently, AMPs/HDPs were shown to have important biological functions, including inducing cell proliferation, migration and differentiation; regulating inflammatory responses; controlling the production of various cytokines/chemokines; promoting wound healing; and improving skin barrier function. Despite the fact that AMPs/HDPs protect our body, several studies have hypothesized that these molecules actively contribute to the pathogenesis of various skin diseases. For example, AMPs/HDPs play crucial roles in the pathological processes of psoriasis, atopic dermatitis, rosacea, acne vulgaris, systemic lupus erythematosus and systemic sclerosis. Thus, AMPs/HDPs may be a double-edged sword, promoting cutaneous immunity while simultaneously initiating the pathogenesis of some skin disorders. This review will describe the most common skin-derived AMPs/HDPs (defensins, cathelicidins, S100 proteins, ribonucleases and dermcidin) and discuss the biology and both the positive and negative aspects of these AMPs/HDPs in skin inflammatory/infectious diseases. Understanding the regulation, functions and mechanisms of AMPs/HDPs may offer new therapeutic opportunities in the treatment of various skin disorders.

The IL-31/IL-31 receptor axis: general features and role in tumor microenvironment

IL-31 is a recently identified cytokine with a well-defined role in the pathogenesis of pruritus. IL-31, whose production is induced by IL-4 and IL-33, binds a heterodimeric receptor (R) composed of the exclusive IL-31RA chain and the shared oncostatin M R. Signaling through the IL-31R involves the MAPK, PI3K/AKT and Jak/STAT pathways. Different variants and isoforms of IL-31RA with different signaling activities have been identified. IL-31 is produced predominantly by circulating Th2 lymphocytes and skin-homing CLA⁺CD45RO⁺ T cells. Studies in humans have demonstrated a pathogenic role for IL-31 in atopic dermatitis and allergic asthma. The first demonstration of the involvement of the IL-31/IL-31R axis in cancer came from studies in patients with mycosis fungoides/Sézary syndrome, the most frequent, cutaneous T cell lymphoma. Tumor cells were shown to produce IL-31, whose serum levels correlated with pruritus intensity. Follicular lymphoma (FL) B cells and their counterparts-germinal center B cells-produced IL-31 and expressed IL-31R, which signaled in the former, but not the latter, cells. IL-31 released in association with microvesicles promoted tumor growth through autocrine/paracrine loops. Malignant mast cells from patients with mastocytosis or Philadelphia-negative myeloproliferative disorder produced IL-31, which contributed to pruritus pathogenesis. Finally, patients with endometrial carcinoma displayed high serum levels of IL-31 and IL-33, which may represent promising disease biomarkers. Targeting strategies for the IL-31/IL-31R axis have been developed, including the CIMM331 humanized anti-human IL-31RA antibody recently tested in a phase I/Ib study.

Human basophils are a source of - and are differentially activated by - IL-31

BACKGROUND

Basophils are important effector cells involved in the pathogenesis of inflammatory skin diseases including chronic urticaria which is associated by increased IL-31 serum levels. So far the effects of IL-31 on human basophils are unknown.

OBJECTIVE

To analyse the functional role of IL-31 in basophil biology.

METHODS

IL-31 expression was evaluated in skin samples derived from chronic spontaneous urticaria patients. Oncostatin M receptor (OSMR), IL-31 receptor A (RA) and IL-31 protein expressions were analysed on human basophils from healthy donors. Basophil responses to IL-31 were assessed for chemotaxis, externalization of CD63 and CD203c as well as the release of histamine, IL-4 and IL-13.

RESULTS

IL-31RA and OSMR were expressed on human basophils. IL-31 was strongly expressed in the skin of patients with chronic spontaneous urticaria and was released from isolated basophils following either anti-IgE, IL-3 or fMLP stimulation. IL-31 induced chemotaxis and the release of IL-4 and IL-13 which was specifically inhibited by anti-IL-31RA and anti-OSMR. Conversely, IL-31 had no effect on CD63 and CD203c externalization or histamine release.

CONCLUSIONS AND CLINICAL RELEVANCE

Human basophils are a source of -and are activated by - IL-31 with the release of pro-inflammatory cytokines and the induction of chemotaxis indicating an important novel function of IL-31 in basophil biology.

The role of human β-defensins in allergic diseases

Antimicrobial peptides (AMPs), also referred to as host defence peptides (HDPs), comprise a large family of small molecules broadly distributed throughout the animal and plant kingdom, historically serving as natural antibiotics. In mammals, there are two major families of AMPs/HDPs, the defensins and the cathelicidins. These peptides have evolved to protect against a wide range of infections from bacteria, viruses, fungi and some parasites. However, in addition to their broad-spectrum killing activities, AMPs/HDPs also possess various biological functions. They activate a variety of cell types, such as keratinocytes, airway epithelial cells and mast cells, among others, and regulate cytokine/chemokine production, cell migration, proliferation, differentiation, angiogenesis, the wound healing process and maintenance of the skin barrier function. Recently, it has become clear that alterations in the level of AMPs/HDPs are associated with the initiation and development of various inflammatory and allergic diseases. In this review, we will discuss the regulation and functions of human β-defensins and outline the current evidence supporting the role of these peptides in the pathogenesis of allergic diseases, including atopic dermatitis, allergic rhinitis, asthma and chronic rhinosinusitis. Understanding the functions and mechanisms of human β-defensins may aid in the development of novel therapeutic strategies for allergic diseases.

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.

Roles of Mas-related G protein-coupled receptor X2 on mast cell-mediated host defense, pseudoallergic drug reactions, and chronic inflammatory diseases

Mast cells (MCs), which are granulated tissue-resident cells of hematopoietic lineage, contribute to vascular homeostasis, innate/adaptive immunity, and wound healing. However, MCs are best known for their roles in allergic and inflammatory diseases, such as anaphylaxis, food allergy, rhinitis, itch, urticaria, atopic dermatitis, and asthma. In addition to the high-affinity IgE receptor (FcεRI), MCs express numerous G protein-coupled receptors (GPCRs), which are the largest group of membrane receptor proteins and the most common targets of drug therapy. Antimicrobial host defense peptides, neuropeptides, major basic protein, eosinophil peroxidase, and many US Food and Drug Administration-approved peptidergic drugs activate human MCs through a novel GPCR known as Mas-related G protein-coupled receptor X2 (MRGPRX2; formerly known as MrgX2). Unique features of MRGPRX2 that distinguish it from other GPCRs include their presence both on the plasma membrane and intracellular sites and their selective expression in MCs. In this article we review the possible roles of MRGPRX2 on host defense, drug-induced anaphylactoid reactions, neurogenic inflammation, pain, itch, and chronic inflammatory diseases, such as urticaria and asthma. We propose that host defense peptides that kill microbes directly and activate MCs through MRGPRX2 could serve as novel GPCR targets to modulate host defense against microbial infection. Furthermore, mAbs or small-molecule inhibitors of MRGPRX2 could be developed for the treatment of MC-dependent allergic and inflammatory disorders.

Role of interleukin-18 in the pathophysiology of allergic diseases

Interleukin (IL)-18 is an IL-1 family cytokine expressed by macrophages, dendritic cells, epithelial cells, and keratinocytes and is implicated in various aspects of both the innate and adaptive immune systems. IL-18 signals similar to IL-1β intracellularly to activate gene transcription. Since its discovery, IL-18 has been demonstrated to play a key role in pathogen defense from helminths and some bacteria. Recently however, evidence has accumulated that IL-18 expression is increased in many presentations of allergic disease. A pathologic role for IL-18 includes stimulating mast cell and basophil degranulation, recruiting granulocytes to sites of inflammation, increasing cytotoxic activity of natural killer (NK) and NK-T cells, inducing Immunoglobulin (Ig)E production and isotype switching, and affecting a broad range of T cells to promote a type II helper T cell (Th2) response. Evidence and importance of these effects are presented, including novel results from our lab implicating IL-18 in the direct expansion of mast cells, basophils, and other myeloid-lineage cells from bone-marrow precursors. The development of urticaria, asthma, dermatitis, rhinitis, and eosinophilic disorders all have demonstrated correlations to increased IL-18 levels either in the tissue or systemically. IL-18 represents a novel site of immune regulation in not only allergic conditions, but also autoimmune diseases and other instances of aberrant immune functioning. Diagrammatic summarized abstract for readers convinance is presented in Fig. 1.

Cationic host defense peptides; novel antimicrobial therapeutics against Category A pathogens and emerging infections

Cationic Host Defense Peptides (HDP, also known as antimicrobial peptides) are crucial components of the innate immune system and possess broad-spectrum antibacterial, antiviral, and immunomodulatory activities. They can contribute to the rapid clearance of biological agents through direct killing of the organisms, inhibition of pro-inflammatory mediators such as lipopolysaccharide, and by modulating the inflammatory response to infection. Category A biological agents and materials, as classified by the United States National Institutes for Health, the US Centers for Disease Control and Prevention, and the US Department of Homeland Security, carry the most severe threat in terms of human health, transmissibility, and preparedness. As such, there is a pressing need for novel frontline approaches for prevention and treatment of diseases caused by these organisms, and exploiting the broad antimicrobial activity exhibited by cationic host defense peptides represents an exciting priority area for clinical research. This review will summarize what is known about the antimicrobial and antiviral effects of the two main families of cationic host defense peptides, cathelicidins, and defensins in the context of Category A biological agents which include, but are not limited to; anthrax (Bacillus anthracis), plague (Yersinia pestis), smallpox (Variola major), tularemia (Francisella tularensis). In addition, we highlight priority areas, particularly emerging viral infections, where more extensive research is urgently required.

Control of the Physical and Antimicrobial Skin Barrier by an IL-31-IL-1 Signaling Network

Atopic dermatitis, a chronic inflammatory skin disease with increasing prevalence, is closely associated with skin barrier defects. A cytokine related to disease severity and inhibition of keratinocyte differentiation is IL-31. To identify its molecular targets, IL-31-dependent gene expression was determined in three-dimensional organotypic skin models. IL-31-regulated genes are involved in the formation of an intact physical skin barrier. Many of these genes were poorly induced during differentiation as a consequence of IL-31 treatment, resulting in increased penetrability to allergens and irritants. Furthermore, studies employing cell-sorted skin equivalents in SCID/NOD mice demonstrated enhanced transepidermal water loss following s.c. administration of IL-31. We identified the IL-1 cytokine network as a downstream effector of IL-31 signaling. Anakinra, an IL-1R antagonist, blocked the IL-31 effects on skin differentiation. In addition to the effects on the physical barrier, IL-31 stimulated the expression of antimicrobial peptides, thereby inhibiting bacterial growth on the three-dimensional organotypic skin models. This was evident already at low doses of IL-31, insufficient to interfere with the physical barrier. Together, these findings demonstrate that IL-31 affects keratinocyte differentiation in multiple ways and that the IL-1 cytokine network is a major downstream effector of IL-31 signaling in deregulating the physical skin barrier. Moreover, by interfering with IL-31, a currently evaluated drug target, we will have to consider that low doses of IL-31 promote the antimicrobial barrier, and thus a complete inhibition of IL-31 signaling may be undesirable.

Expression of Beta-Defensin 131 Promotes an Innate Immune Response in Human Prostate Epithelial Cells

Previously, using the Illumina HumanHT-12 microarray we found that β-defensin 131 (DEFB131), an antimicrobial peptide, is upregulated in the human prostate epithelial cell line RWPE-1 upon stimulation with lipoteichoic acid (LTA; a gram-positive bacterial component), than that in the untreated RWPE-1 cells. In the current study, we aimed to investigate the role of DEFB131 in RWPE-1 cells during bacterial infection. We examined the intracellular signaling pathways and nuclear responses in RWPE-1 cells that contribute to DEFB131 gene induction upon stimulation with LTA. Chromatin immunoprecipitation was performed to determine whether NF-κB directly binds to the DEFB131 promoter after LTA stimulation in RWPE-1 cells. We found that DEFB131 expression was induced by LTA stimulation through TLR2 and p38MAPK/NF-κB activation, which was evident in the phosphorylation of both p38MAPK and IκBα. We also found that SB203580 and Bay11-7082, inhibitors of p38MAPK and NF-κB, respectively, suppressed LTA-induced DEFB131 expression. The chromatin immunoprecipitation assay showed that NF-κB directly binds to the DEFB131 promoter, suggesting that NF-κB is a direct regulator, and is necessary for LTA-induced DEFB131 expression in RWPE-1 cells. Interestingly, with DEFB131 overexpression in RWPE-1 cells, the accumulation of mRNA and protein secretion of cytokines (IL-1α, IL-1β, IL-6, and IL-12α) and chemokines (CCL20, CCL22, and CXCL8) were significantly enhanced. In addition, DEFB131-transfected RWPE-1 cells markedly induced chemotactic activity in THP-1 monocytes. We concluded that DEFB131 induces cytokine and chemokine upregulation through the TLR2/NF-κB signaling pathway in RWPE-1 cells during bacterial infection and promotes an innate immune response.

Cathelicidin modulates the function of monocytes/macrophages via the P2X7 receptor in a teleost, Plecoglossus altivelis

Cathelicidins (CATHs) are a family of endogenous antimicrobial peptides that are capable of both direct bacteria-killing and immunomodulatory effects. P2X7 receptor (P2X7R) is a mediator of CATH in mammalian immune cells. Here, we studied the function and regulation of CATH in head kidney-derived monocytes/macrophages (MO/MФ) from ayu, Plecoglossus altivelis. We investigated the chemotaxis of MO/MФ in response to ayu CATH (PaCATH), and found that PaCATH had a dose-dependent effect on MO/MФ chemotaxis with the optimal concentration of 10.0 μg/ml. The qPCR and Western blot analysis revealed that PaCATH inhibited the expression of ayu P2X7R (PaP2X7R) at both mRNA and protein levels. Knockdown of the PaP2X7R expression in ayu MO/MФ by RNA interference not only significantly inhibited the chemotactic effect of PaCATH on MO/MФ, but also obviously reduced the effect of PaCATH on the phagocytosis, bacteria-killing, respiratory burst, and cytokine expression of ayu MO/MФ. Our study revealed that the immunomodulatory effect of fish CATH is mediated by P2X7R.

The frequencies of haplotypes defined by three polymorphisms of the IL-31 gene: -1066, -2057, and IVS2+12 in Polish patients with atopic dermatitis

BACKGROUND

Severe pruritus is one of the cardinal symptoms of atopic dermatitis (AD). Recently, the interleukin (IL)-31 cytokine has been implicated in the induction and maintenance of severe pruritus and chronic skin inflammation in several pruritic skin diseases, including AD.

OBJECTIVE

We aimed to investigate the association of the IL-31 gene haplotypes with pruritus and severity of AD, as well as their correlation to the serum IL-31 levels.

METHODS

A total of 127 patients with AD and 96 healthy controls were analyzed for polymorphic variants of the IL-31 gene using an amplification refractory mutation system-polymerase chain reaction method. IL-31 haplotype frequencies were estimated with the use of tagging single nucleotide polymorphisms, expectation-maximization, and Excoffier-Laval-Balding algorithms. Serum IL-31 levels were measured using a standard enzyme-linked immunosorbent assay kit.

RESULTS

The frequency of AAG, AGA, AGG, and GAA haplotypes of the IL-31 gene was higher in patients with AD than in controls. The mean IL-31 levels in serum were lower in controls than in the patients (P < 0.00001) and were higher in those with severe vs. mild AD (P = 0.008). No correlation was found between IL-31 and the severity of pruritus. The haplotype AAA was associated with a high IL-31 serum level (P = 0.008) and with severe AD (high SCORing Atopic Dermatitis index) (P = 0.013). The haplotype GAA was associated with a severe form of pruritus (P = 0.016) and the haplotype GGG with the mild one (P = 0.07).

CONCLUSION

The results of this study suggest that the severity of AD in a Polish population is associated with some specific haplotypes of the IL-31 gene, which can indicate their prognostic role also renews the questions concerning the role of IL-31 in pruritus in AD.

Unique features of human cathelicidin LL-37

Cathelicidins are antimicrobial peptides produced by humans and animals in response to various pathogenic microbes. This review intends to provide a brief overview of the expression, structure, properties and function of human cathelicidin LL-37 which may be a therapeutic agent against a variety of bacterial and viral diseases, cancers, and hard-to-heal wounds. Cathelicidins act as a primary defense against bacteria and other pathogens in the case of inflammation. They are able to kill bacteria and fungi, inhibit and destroy bacterial biofilms, and possess antiviral and antiparasitics properties. They can also play a role in angiogenesis, wound healing, and the regulation of apoptosis. The host defense peptide LL-37 has emerged as a novel modulator of tumor growth and metastasis in carcinogenesis of various types of cancers. LL-37 is an antimicrobial peptide able of inducing various effects. It acts as an anti- and pro- inflammatory factor. Cathelicidins are able to directly and selectively destroy membranes of various microbes and cancer cells, but they do not attack normal cells. The role of cathelicidins in cancer is double-sided. They play an important role in killing cancer cells and may provide a new possibility for the development of cancer therapeutics. However, they also can participate in carcinogenesis. Due to its activity spectrum LL-37 could be applied in pharmacotherapy. Cathelicidin peptides could serve as a template for the development of modern anti-microbial and anti-viral drugs. LL-37 is an excellent candidate to develop into therapeutics for infected wounds.

Short, Synthetic Cationic Peptides Have Antibacterial Activity against Mycobacterium smegmatis by Forming Pores in Membrane and Synergizing with Antibiotics

Multicellular organisms are constantly exposed to a multitude of pathogenic microbes. Infection is inhibited in vivo by the innate and adaptive immune system. Mycobacterium species have emerged that are resistant to most antibiotics. We identified several naturally occurring cationic antimicrobial peptides that were active at low micromolar concentrations against Mycobacterium smegmatis. Human-derived cathelicidin LL-37 is well characterized and studied against M. smegmatis; we compared LL-37 with Chinese cobra-derived cathelicidin NA-CATH and mouse cathelicidin (mCRAMP). Two synthetic 11-residue peptides (ATRA-1A and ATRA-2) containing variations of a repeated motif within NA-CATH were tested for their activity against M. smegmatis along with a short synthetic peptide derivative from the human beta-defensin hBD3 (hBD3-Pep4). We hypothesized that these smaller synthetic peptides may demonstrate antimicrobial effectiveness with shorter length (and at less cost), making them strong potential candidates for development into broad-spectrum antimicrobial compounds or use in combination with antibiotics. These peptides have antimicrobial activity with EC50 ranging from 0.05 to 1.88 μg/mL against Mycobacterium smegmatis. The ATRA-1A short peptide was found to be the most effective antimicrobial peptide (AMP) (EC50 = 0.05 μg/mL). High bactericidal activity correlated with bacterial membrane depolarization and permeabilization activities. The efficacy of the peptides was further analyzed through Minimal Inhibitory Concentration (MIC) assays. The MICs were determined by the microdilution method. The peptide mCRAMP showed the best MIC activity at 15.6 μg/mL. Neither of the effective short synthetic peptides demonstrated synergy with the antibiotic rifampicin, although both demonstrated synergy with the cyclic peptide antibiotic polymyxin B. The peptides LL-37 and mCRAMP displayed synergism with rifampicin in MIC assays, whereas antibiotic polymyxin B displayed synergism with LL-37, ATRA-1A, and hBD3-Pep4. In further studies, polymyxin B synergized with LL-37, ATRA-1A, and hBD3-Pep4 while Rifampicin synergized with LL-37 and mCRAMP for intracellular killing of mycobacteria residing inside macrophages. These studies provide the foundation for the potential development of synthetic cationic antimicrobial peptides with activity against mycobacteria.

Cathelicidin impact on inflammatory cells

Cathelicidins, like other antimicrobial peptides, exhibit direct antimicrobial activities against a broad spectrum of microbes, including both Gram-positive and Gram-negative bacteria, enveloped viruses, and fungi. These host-derived peptides kill the invaded pathogens by perturbing their cell membranes and can neutralize biological activities of endotoxin. Nowadays, more and more data indicate that these peptides, in addition to their antimicrobial properties, possess various immunomodulatory activities. Cathelicidins have the potential to influence and modulate, both directly and indirectly, the activity of various cell populations involved in inflammatory processes and in host defense against invading pathogens. They induce migration of neutrophils, monocytes/macrophages, eosinophils, and mast cells and prolong the lifespan of neutrophils. These peptides directly activate inflammatory cells to production and release of different pro-inflammatory and immunoregulatory mediators, cytokines, and chemokines, however cathelicidins might mediate the generation of anti-inflammatory cytokines as well. Cathelicidins also modulate epithelial cell/keratinocyte responses to infecting pathogens. What is more, they affect activity of monocytes, dendritic cells, keratinocytes, or epithelial cells acting in synergy with cytokines or β-defensins. In addition, these peptides indirectly balance TLR-mediated responses of monocytes, macrophages, dendritic cells, epithelial cells, and keratinocytes. This review discusses the role and significance of cathelicidins in inflammation and innate immunity against pathogens.

Past, present, and future for biologic intervention in atopic dermatitis

Atopic dermatitis (AD) is a debilitating disease that significantly alters the quality of life for one in four children and one in 10 adults. Current management of AD utilizes combinations of treatments to symptomatically alleviate disease by suppressing the inflammatory response and restoring barrier function in the skin, reducing disease exacerbation and flare, and preventing secondary skin infections. Resolution is temporary and long-term usage of these treatments can be associated with significant side-effects. Antibody therapies previously approved for inflammatory diseases have been opportunistically evaluated in patients with atopic dermatitis; however, they often failed to demonstrate a significant clinical benefit. Monoclonal antibodies currently in development offer hope to those individuals suffering from the disease by specifically targeting immune and molecular pathways important for the pathogenesis of atopic dermatitis. Here, we review the underlying biological pathways and the state of the art in therapeutics in AD.

Role of cytokines and chemokines in itch

Cytokines classically are secreted "messenger" proteins that modulate cellular function of immune cells. Chemokines attract immune cells to the site where they exert various functions in inflammation, autoimmunity or cancer. Increasing evidence is emerging that cytokines or chemokines can act as "neuro-modulators" by activating high-affinity receptors on peripheral or central neurons, microglia cells or Schwann cells. Very recently, cytokines have been shown to act as pruritogens in rodents and humans, while a role of chemokines in itch has thus far been only demonstrated in mice. Upon stimulation, cytokines are released by skin or immune cells and form a "bridge of communication" between the immune and nervous system. For some cytokines such as IL-31 and TSLP, the evidence for this role is strong in rodents. For cytokines such as IL-4, there is some convincing evidence, while for cytokines such as oncostatin M, IL-2, IL-6, IL-8 and IL-13, direct evidence is currently limited. Current clinical trials support the idea that cytokines and chemokines and their receptors or signalling pathways are promising targets for the future therapy of certain subtypes of itch.

Reduced filaggrin expression is accompanied by increased Staphylococcus aureus colonization of epidermal skin models

BACKGROUND

Atopic dermatitis is an inflammatory skin disease that is characterized by a reduced skin barrier function, reduced filaggrin (FLG) expression as well as increased colonization by Staphylococcus aureus.

OBJECTIVE

This study focused on the possible involvement of FLG in epidermal colonization by S. aureus and/or whether it affects the epidermal defence mechanisms, including the expression of antimicrobial peptides (AMPs) and enzymes involved in stratum corneum barrier lipid synthesis. Furthermore, IL-31 has been shown to reduce FLG expression, but its effects on bacterial colonization and on the expression of AMPs and enzymes involved in the barrier lipid synthesis are not known.

MATERIAL AND METHODS

We established N/TERT-based epidermal models (NEMs), after FLG knockdown (FLG-KD) and/or cultured with IL-31, that were colonized with S. aureus for 24 h.

RESULTS

Both FLG-KD and IL-31 supplementation resulted in significantly increased epidermal S. aureus colonization, as well as in an up-regulation of S. aureus-induced IL-8 expression. IL-31, but not FLG-KD, prevented S. aureus-induced up-regulation of mRNA expression for the AMPs human β-defensin 2 and -3 and RNAse7, whereas psoriasin expression remained unchanged. Furthermore, the S. aureus colonization induced changes in mRNA expression of ELOVL4 was not affected by FLG-KD, but was blocked by IL-31. Expression of SCD-1 and Gcase mRNA was reduced by IL-31, but not by FLG-KD.

CONCLUSION

This study shows that NEMs, with FLG-KD and/or cultured in the presence of IL-31, mimic the skin of patients with atopic dermatitis in several aspects, including enhanced bacterial colonization, increased inflammatory and reduced protective responses.

Current treatment options in patients with mastocytosis: status in 2015 and future perspectives

Mastocytosis is a term referring to a heterogeneous group of disorders characterized by abnormal mast cell (MC) accumulation in the skin and/or internal organs. In children, the disease involves mostly the skin (cutaneous mastocytosis; CM), whereas in adults, the disease is usually systemic (systemic mastocytosis; SM). Advanced SM variants with end-organ damage and reduced life expectancy have also been described, but are rare. Clinical signs and symptoms in SM result from excessive mediator release by MCs and, in aggressive forms, from organ failure related to MC infiltration. As a consequence, treatment of indolent SM aims primarily at the control of symptoms caused by MC mediator release. By contrast, in advanced SM, such as aggressive SM, MC leukemia, and MC sarcoma, intensive (chemo)therapy with or without allogeneic stem cell transplantation has to be considered. In addition, activating mutations in KIT (mostly KIT D816V in adults) are found in most patients with SM, so that targeted therapies aimed at blocking mutant KIT variants or/and downstream signaling pathways are currently being developed. Other targets, such as specific surface antigens expressed on neoplastic MCs, might be considered for the development of future therapies in advanced SM.

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.