Chanisa Kiatsurayanon

Host Defense (Antimicrobial) Peptide, Human β-Defensin-3, Improves the Function of the Epithelial Tight-Junction Barrier in Human Keratinocytes

Human β-defensins (hBDs) are host defense peptides that not only exhibit microbicidal properties but also stimulate various cellular activities, including keratinocyte proliferation, migration, and wound healing. hBDs are overexpressed in the skin in cases of psoriasis but are downregulated in atopic dermatitis skin, although both diseases are associated with stratum corneum barrier defects. Because the tight-junction (TJ) barrier is also dysfunctional in both atopic dermatitis and psoriasis patients, we hypothesized that hBDs may regulate the TJ barrier function in keratinocytes. We observed that, among the hBDs tested, only hBD-3 increased the expression of several claudins and their localization along the cell-cell borders. In addition, hBD-3 elevated the transepithelial electrical resistance and reduced the paracellular permeability of keratinocyte layers, and this effect was reversed by the claudin inhibitor ochratoxin A, CCR6 antibody, and CCR6 small interfering RNA. Moreover, hBD-3 enhanced the activation of Rac1, atypical protein kinase C, glycogen synthase kinase-3, and phosphatidylinositol 3 kinase, which are required for the hBD-3-mediated regulation of the TJ barrier function, as evidenced by the effects of their respective inhibitors. Collectively, our findings provide evidence regarding the contribution of host defense peptides to the innate immunity of skin by regulating TJ barrier function, in addition to their antimicrobial and other immunomodulatory activities.

The Human Cathelicidin LL-37 Host Defense Peptide Upregulates Tight Junction-Related Proteins and Increases Human Epidermal Keratinocyte Barrier Function

Both psoriasis and atopic dermatitis (AD) are not only associated with an impaired stratum corneum barrier, but also with abnormal expression of the tight junction (TJ) proteins. Because host defense peptides, including LL-37, are overexpressed in lesional psoriatic skin but are downregulated in lesional AD skin, we hypothesized that LL-37 might regulate the TJ function in keratinocytes. We demonstrated that LL-37 selectively increased the expression of several claudins and occludin, and enhanced their membrane distribution. Furthermore, LL-37 elevated the transepithelial electrical resistance while reducing the paracellular permeability of keratinocyte layers, and this activity was weakened by the claudin inhibitor ochratoxin A. A characterization of the molecular mechanism underlying the regulation of the TJ barrier by LL-37 revealed that LL-37 induced the activation of the Rac1, atypical PKC, glycogen synthase kinase-3 and PI3K pathways, and the specific inhibition of these pathways reversed the LL-37-mediated regulation of TJ function. In addition, LL-37 enhanced the expression of differentiation markers under the control of ochratoxin A, suggesting an association between LL-37-induced TJ function and keratinocyte differentiation. These data provide novel evidence that, in addition to its antimicrobial and other immunoregulatory functions, LL-37 contributes to cutaneous immunity by strengthening the skins barrier function.

The antimicrobial protein S100A7/psoriasin enhances the expression of keratinocyte differentiation markers and strengthens the skin's tight junction barrier

S100A7/psoriasin is a member of the S100 protein family and is encoded in the epidermal differentiation complex, which contains genes for markers of epidermal differentiation. S100A7/psoriasin is overexpressed in hyperproliferative skin diseases, where it is believed not only to exhibit antimicrobial functions, but also to induce immunomodulatory activities, including chemotaxis and cytokine/chemokine production.

Human β-defensin-3 increases the expression of interleukin-37 through CCR6 in human keratinocytes

BACKGROUND Interleukin (IL)-37, a new member of the IL-1 family, is characterized as a fundamental inhibitor of innate immunity: it dampens the production of proinflammatory cytokines, protects against inflammatory and autoimmune diseases, and plays a potent immunosuppressive role in the pathogenesis of psoriasis. IL-37 is highly expressed in psoriatic skin, in which human β-defensins (hBDs) have been detected. Although hBDs enhance the production of cytokines, including IL-1 cytokines, whether they stimulate the production of IL-37 remains unclear. OBJECTIVES To assess the ability of hBDs to stimulate IL-37 expression/production by human keratinocytes and to determine the mechanism involved. METHODS Real-time PCR and Western blotting were used to evaluate IL-37 expression. Caspase activities were assessed using colorimetric assay kits. A CCR6 antibody, siRNA, and caspase, Smad3, MAPK and NF-κB inhibitors were used to investigate the signaling mechanism of hBDs. RESULTS Among the four hBDs used, only hBD-3 up-regulated the mRNA and protein expression of IL-37. The combination of TNF-α, EGF and poly (I:C) with hBD-3 synergistically enhanced the mRNA but not the protein expression of IL-37. Furthermore, hBD-3 increased the release of IL-37 into the culture supernatants. Evaluation of the signaling mechanism of hBD-3 suggested that caspases 1 and 4, Smad3, CCR6, MAPKs and NF-κB were required for hBD-3-mediated IL-37 expression. CONCLUSIONS The finding that hBD-3 stimulates IL-37 expression, a novel target for the pathogenesis and therapy of cutaneous inflammatory diseases, provides evidence that hBDs contribute to the suppression of inflammatory and innate immune responses through the regulation of IL-37 expression.

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.

Interleukin-36 cytokines enhance the production of host defense peptides psoriasin and LL-37 by human keratinocytes through activation of MAPKs and NF-κB

Our skin is continuously exposed to potential pathogens and plays a crucial role in initiating immune responses to eliminate these microorganisms. Skin-derived host defense peptides (HDPs) or antimicrobial peptides, such as b-defensins, LL-37 and psoriasin (S100A7), provide a direct front-line component of skin innate immunity [1,2]. In addition to their antimicrobial properties, HDPs activate various immune/inflammatory cells, including neutrophils, mast cells, lymphocytes, monocytes and macrophages [1,2]. They also regulate immunomodulatory activities in keratinocytes, including the enhancement of cytokine/chemokine production, chemotaxis, cell proliferation and wound healing [1,2]. Interleukin (IL)-36a (formerly known as IL-1F6), IL-36b (IL-1F8) and IL-36g (IL-1F9) are recently discovered new members of the IL-1 family [3]. Similar to the classical IL-1 cytokines (IL-1a, IL-b and IL-18), IL-36s participate in the initiation and/or regulation of immune responses [3]. These cytokines and their heterodimeric receptor are particularly expressed at high levels in epithelial cells and keratinocytes in models of contact hypersensitivity, infection with herpes simplex virus 1, and psoriatic skin [4,5], suggesting IL36 roles in skin immunity. Furthermore, it has recently been demonstrated that transgenic mice overexpressing IL-36a exhibit inflammatory skin lesions that share the same features as psoriasis [4,5]. Because psoriatic skin overproduces HDPs, such as psoriasin and LL-37, and because these HDPs are involved in the regulation of skin immunity [1,2], we hypothesized that IL-36s might stimulate keratinocytes to produce psoriasin and LL-37, thereby participating in the regulation of the cutaneous immune system. Normal human keratinocytes were cultured in HuMedia-KG2 and stimulated with IL-1b, IL-36a, IL-36b or IL-36g. Total RNA extraction, real-time PCR, ELISA and Western blot were carried out as described previously [6]. As shown in Fig. 1(a), IL-36a, IL36b and IL-36g significantly increased the gene expression levels of psoriasin and LL-37. In preliminary experiments, the mRNA expression of psoriasin peaked within 48 h and LL-37 peaked within 12 h after exposure to IL-36s. Because IL-36s dramatically enhanced the mRNA expression of psoriasin and LL37, we predicted that they would trigger a corresponding increase in the protein production of both HDPs. Using appropriate ELISAs, we demonstrated that IL-36s markedly increased the production of psoriasin and LL-37 (Fig. 1(b)). Because IL-1b also induces HDP expression in keratinocytes [1,2], we compared the potencies of IL-1b and IL-36 in inducing the expression and production of psoriasin and LL-37. IL-1b and IL-36a showed comparable potencies, whereas IL-36b and IL36g were more efficient than IL-1b used at 20 ng/ml, the

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.

The Role of Host Defense Peptide Human β-defensins in the Maintenance of Skin Barriers

The epidermis functions as a first-line defense barrier that protects the body from the external environment. As a chemical hindrance, the epidermis possesses acidic pH, highly organized lipids and various host defense peptides, also known as antimicrobial peptides. Human β-defensins (hBDs), one of the most important host defense peptide families found in our skin, are well-known for their broad-spectrum microbicidal activities. However, there is a growing body of evidence indicating that hBDs also orchestrate several immunomodulatory functions and are the cornerstone that bridges the innate and adaptive immune responses during skin inflammation and infection. Moreover, recent work identified the potential role of hBDs in the regulation and maintenance of the skin barrier function. In this review, we describe the current knowledge concerning the role of hBDs in skin barriers and discuss the potential clinical implications of these peptides in cutaneous biology. Understanding the roles of hBDs in the regulation and maintenance of skin barriers may aid in the development of novel therapeutic strategies for skin conditions where the skin barrier is impaired, such as atopic dermatitis and psoriasis.

Unilateral Linear Punctate Palmoplantar Keratoderma: A Case Report

Punctate palmoplantar keratoderma (PPPK) is a rare entity with an estimated prevalence rate of 1.17/100,000. PPPK usually presents with bilateral asymptomatic, tiny, hyperkeratotic punctate papules and plaques on the palmoplantar surface. Among the PPPK varieties, the linear presentation is much rarer, and so far there have been only 3 case reports. Here, we report the case of a 27-year-old female Thai patient who presented to our outpatient clinic with unilateral asymptomatic linear thickening lesions on her right sole since childhood. There were no similar lesions on other parts of the body. A histopathologic examination revealed epidermal hyperplasia and hyperkeratosis without columns of parakeratosis or cornoid lamella. The other examinations were normal. The clinical and histological contexts were consistent with a diagnosis of unilateral linear PPPK. The patient was treated with topical 10% urea cream and 10% salicylic acid cream twice daily. To the best of our knowledge, this is the first reported case of unilateral linear PPPK in Thailand, and the fourth reported case worldwide.

The antimicrobial peptide derived from insulin-like growth factor-binding protein 5, AMP-IBP5, regulates keratinocyte functions through Mas-related gene X receptors

BACKGROUND In addition to their microbicidal properties, host defense peptides (HDPs) display various immunomodulatory functions, including keratinocyte production of cytokines/chemokines, proliferation, migration and wound healing. Recently, a novel HDP named AMP-IBP5 (antimicrobial peptide derived from insulin-like growth factor-binding protein 5) was shown to exhibit antimicrobial activity against numerous pathogens, even at concentrations comparable to those of human β-defensins and LL-37. However, the immunomodulatory role of AMP-IBP5 in cutaneous tissue remains unknown. OBJECTIVES To investigate whether AMP-IBP5 triggers keratinocyte activation and to clarify its mechanism. METHODS Production of cytokines/chemokines and growth factors was determined by appropriate ELISA kits. Cell migration was assessed by in vitro wound closure assay, whereas cell proliferation was analyzed using BrdU incorporation assay complimented with XTT assay. MAPK and NF-κB activation was determined by Western blotting. Intracellular cAMP levels were assessed using cAMP enzyme immunoassay kit. RESULTS Among various cytokines/chemokines and growth factors tested, AMP-IBP5 selectively increased the production of IL-8 and VEGF. Moreover, AMP-IBP5 markedly enhanced keratinocyte migration and proliferation. AMP-IBP5-induced keratinocyte activation was mediated by Mrg X1-X4 receptors with MAPK and NF-κB pathways working downstream, as evidenced by the inhibitory effects of MrgX1-X4 siRNAs and ERK-, JNK-, p38- and NF-κB-specific inhibitors. We confirmed that AMP-IBP5 indeed induced MAPK and NF-κB activation. Furthermore, AMP-IBP5-induced VEGF but not IL-8 production correlated with an increase in intracellular cAMP. CONCLUSIONS Our findings suggest that in addition to its antimicrobial function, AMP-IBP5 might contribute to wound healing process through activation of keratinocytes.