Innate immune defense of the nail unit by antimicrobial peptides

Antifungal properties of cathelicidin LL-37: current knowledge and future research directions

The threat of fungal diseases is substantially underestimated worldwide, but they have serious consequences for humans, animals, and plants. Given the limited number of existing antifungal drugs together with the emergence of drug-resistant strains, many researchers have actively sought alternatives or adjuvants to antimycotics. The best way to tackle these issues is to unearth potential antifungal agents with new modes of action. Antimicrobial peptides are being hailed as a promising source of novel antimicrobials since they exhibit rapid and broad-spectrum microbicidal activities with a reduced likelihood of developing drug resistance. Recent years have witnessed an explosion in knowledge on microbicidal activity of LL-37, the sole human cathelicidin. Herein, we provide a summary of the current understanding about antifungal properties of LL-37, with particular emphasis on its molecular mechanisms. We further illustrate fruitful areas for future research. LL-37 is able to inhibit the growth of clinically and agronomically relevant fungi including Aspergillus, Candida, Colletotrichum, Fusarium, Malassezia, Pythium, and Trichophyton. Destruction of the cell wall integrity, membrane permeabilization, induction of oxidative stress, disruption of endoplasmic reticulum homeostasis, formation of autophagy-like structures, alterations in expression of numerous fungal genes, and inhibition of cell cycle progression are the key mechanisms underlying antifungal effects of LL-37. Burgeoning evidence also suggests that LL-37 may act as a potential anti-virulence peptide. It is hoped that this review will not only motivate researchers to conduct more detailed studies in this field, but also inspire further innovations in the design of LL-37-based drugs for the treatment of fungal infections.

Keratinocytes: An Enigmatic Factor in Atopic Dermatitis

Atopic dermatitis (AD), characterized by rashes, itching, and pruritus, is a chronic inflammatory condition of the skin with a marked infiltration of inflammatory cells into the lesion. It usually commences in early childhood and coexists with other atopic diseases such as allergic rhinitis, bronchial asthma, allergic conjunctivitis, etc. With a prevalence rate of 1–20% in adults and children worldwide, AD is gradually becoming a major health concern. Immunological aspects have been frequently focused on in the pathogenesis of AD, including the role of the epidermal barrier and the consequent abnormal cytokine expressions. Disrupted epidermal barriers, as well as allergic triggers (food allergy), contact allergens, irritants, microbes, aggravating factors, and ultraviolet light directly initiate the inflammatory response by inducing epidermal keratinocytes, resulting in the abnormal release of various pro-inflammatory mediators, inflammatory cytokines, and chemokines from keratinocytes. In addition, abnormal proteinases, gene mutations, or single nucleotide polymorphisms (SNP) affecting the function of the epidermal barrier can also contribute towards disease pathophysiology. Apart from this, imbalances in cholinergic or adrenergic responses in the epidermis or the role played by immune cells in the epidermis such as Langerhans cells or antigen-presenting cells can also aggravate pathophysiology. The dearth of specific biomarkers for proper diagnosis and the lack of a permanent cure for AD necessitate investigation in this area. In this context, the widespread role played by keratinocytes in the pathogenesis of AD will be reviewed in this article to facilitate the opening up of new avenues of treatment for AD.

Coexistence of onychomycosis and nail psoriasis and its correlation with systemic treatment

BACKGROUND

Epidemiological studies indicate that onychomycosis may affect up to 79% of psoriatic patients. Onychomycosis in psoriatic patients is more commonly caused by yeasts comparing with non-psoriatic.

OBJECTIVES

Evaluate the prevalence of fungi in nail psoriasis. Evaluate the association between direct mycological examination (DME) and mycological culture, Nail Psoriasis Severity Index (NAPSI) and systemic treatment for psoriasis.

METHODS

Of 133 nails from 20 patients with nail psoriasis were evaluated as follows: 9 patients were using topical treatment and 11 were on systemic treatment. The assessment of psoriasis severity using NAPSI was performed in all psoriatic nails. The presence of fungi was confirmed in DME and culture.

RESULTS

DME showed the presence of fungal elements in 45 nails (33.83%) with a predominance of blastoconidia (95.5%) No septate hyphae were seen. Mycological culture was positive in 36 (27.06%) samples. Among them, Candida grew in 31 (86.1%): Candida parapsilosis in 15 (48.38%), Candida spp in 14 (45.16%). No growth of dermatophytes was observed. Patients with systemic treatment showed a higher frequency of positive test (DME and culture) for fungi when compared to topic treatment (p:.006). There was a positive correlation between NAPSI, mycological culture and systemic treatment (p:.0063); the risk was four times higher (OR:4.0).

LIMITATION OF THE STUDY

Sample size.

CONCLUSION

These results are consistent with some previous reports, Candida was the fungus with higher frequency on the psoriatic nails, however, the role of these fungi is controversial (contamination x colonisation x infection). The fact that the immunosuppressive treatment increases the chance of fungal infection leads us to a greater attention to this patient profile, to prevent the intensification of nail psoriasis (Köbner phenomenon).

Overview of the molecular determinants contributing to the expression of Psoriasis and Psoriatic Arthritis phenotypes

Psoriasis and psoriatic arthritis are multifactorial chronic disorders whose etiopathogenesis essentially derives from the alteration of several signalling pathways and the co-occurrence of genetic, epigenetic and non-genetic susceptibility factors that altogether affect the functional and structural property of the skin. Although shared and differential susceptibility genes and molecular pathways are known to contribute to the onset of pathological phenotypes, further research is needed to dissect the molecular causes of psoriatic disease and its progression towards Psoriatic Arthritis. This review will therefore be addressed to explore differences and similarities in the etiopathogenesis and progression of both disorders, with a particular focus on genes involved in the maintenance of the skin structure and integrity (keratins and collagens), modulation of patterns of recognition (through Toll-like receptors and dectin-1) and immuno-inflammatory response (by NLRP3-dependent inflammasome) to microbial pathogens. In addition, special emphasis will be given to the contribution of epigenetic elements (methylation pattern, non-coding RNAs, chromatin modifiers and 3D genome organization) to the etiopathogenesis and progression of psoriasis and psoriatic arthritis. The evidence discussed in this review highlights how the knowledge of patients' clinical and (epi)genomic make-up could be helpful for improving the available therapeutic strategies for psoriasis and psoriatic arthritis treatment.

NP213 (Novexatin®): A unique therapy candidate for onychomycosis with a differentiated safety and efficacy profile

NP213 (Novexatin®) is a novel antifungal peptide specifically designed for the topical treatment of onychomycosis. NP213 was designed using host defense peptides (HDP), essential components of the innate immune response to infection, as a template. NP213 is a water-soluble cyclic fungicidal peptide that effectively penetrates human nail. NP213 demonstrated a promising preclinical and clinical safety profile, with no evidence of systemic exposure following topical application to the skin and nails. NP213 was efficacious in two phase IIa human trials with 43.3% of patients having no fungi detectable by culture of fragments from NP213-treated nails after 180 days in the first study and likewise 56.5% of patients were culture negative for dermatophytes after 360 days in the second phase IIa study. In both trials, NP213 was applied daily for only 28 days in marked contrast to other topical onychomycosis treatments that require application for up to 52 weeks. Patient reported outcomes from the phase IIa studies were positive with participants recording an improved appearance of their nails after only 14 days of application. All fungi identified in these studies were Trichophyton spp. NP213 (Novexatin®) is a promising, highly differentiated peptide-based candidate for the topical treatment of onychomycosis, addressing the infectious cause and cosmetic issues of this very common condition.

Innate Inspiration: Antifungal Peptides and Other Immunotherapeutics From the Host Immune Response

The purpose of this review is to describe antifungal therapeutic candidates in preclinical and clinical development derived from, or directly influenced by, the immune system, with a specific focus on antimicrobial peptides (AMP). Although the focus of this review is AMP with direct antimicrobial effects on fungi, we will also discuss compounds with direct antifungal activity, including monoclonal antibodies (mAb), as well as immunomodulatory molecules that can enhance the immune response to fungal infection, including immunomodulatory AMP, vaccines, checkpoint inhibitors, interferon and colony stimulating factors as well as immune cell therapies. The focus of this manuscript will be a non-exhaustive review of antifungal compounds in preclinical and clinical development that are based on the principles of immunology and the authors acknowledge the incredible amount of in vitro and in vivo work that has been conducted to develop such therapeutic candidates.

A Stealthy Fungal Attack Requires an Equally Clandestine Approach to Onychomycosis Treatment

Onychomycosis is a chronic fungal infection of the nail that is recalcitrant to treatment. It is unclear why normally effective antifungal therapy results in low cure rates. Evidence suggests that there may be a plethora of reasons that include the limited immune presence in the nail, reduced circulation, presence of commensal microbes, and fungal influence on immune signaling. Therefore, treatment should be designed to address these possibilities and work synergistically with both the innate and adaptive immune responses.

Improved Methods for Assessing Therapeutic Potential of Antifungal Agents against Dermatophytes and Their Application in the Development of NP213, a Novel Onychomycosis Therapy Candidate

Onychomycosis is a common, difficult-to-treat nail infection that is mainly caused by dermatophytes. Current therapies are not wholly effective and are associated with manifold side effects.

Onychomycosis is a common, difficult-to-treat nail infection that is mainly caused by dermatophytes. Current therapies are not wholly effective and are associated with manifold side effects. The development of treatments for onychomycosis is challenging because standard in vitro tests are not predictive of antifungal efficacy within the nail. We have developed a new antifungal agent, NP213, for the treatment of onychomycosis. NP213 is based on endogenous host defense peptides produced within the nail. We compared the in vitro activity of NP213 and existing antifungal agents using conventional antimicrobial susceptibility test (AST) systems and more physiologically relevant models based on the human nail. We observed that the standard in vitro AST methodologies failed to predict the efficacy of antifungal agents within the nail. To address that, we present a more physiologically relevant modified AST method. This method, alongside other standard in vitro assessments of activity (including mechanism-of-action and time-of-kill studies), better reflected the activity of NP213 and other antifungal agents within the nail than standard in vitro AST methods. NP213 is a rapidly acting, fungicidal peptide that is superior to existing antifungal agents in vitro. It penetrated the nail more effectively than other antifungals, as confirmed by using an optimized in vitro nail infection model. The data presented here support the current clinical development status of NP213 as a novel agent for treating onychomycosis. We propose that the modified tests developed and applied for NP213 characterization are the most relevant to use for screening any potential therapeutic candidates for onychomycosis.

Antimicrobial and immunomodulatory activity of host defense peptides, clavanins and LL-37, in vitro: An endodontic perspective

Endodontic treatment is mainly based on root canal disinfection and its failure may be motivated by microbial resistance. Endodontic therapy can be benefitted by host defense peptides (HDPs), which are multifunctional molecules that act against persistent infection and inflammation. This study aimed to evaluate the antimicrobial, cytotoxic and immunomodulatory activity of several HDPs, namely clavanin A, clavanin A modified (MO) and LL-37, compared to intracanal medication Ca(OH)₂. HDPs and Ca(OH)₂ were evaluated by: (1) antimicrobial assays against Candida albicans and Enterococcus faecalis, (2) cytotoxicity assays and (3) cytokine tumor necrosis factor (TNF)-α, monocyte chemoattractant protein (MCP)-1, interleukin (IL)-1α, IL-6, IL-10 and IL-12 and nitric oxide (NO) production by RAW 264.7 cells incubated with or without heat-killed (HK) C. albicans or E. faecalis combined or not with interferon-γ. The minimum inhibitory concentration (MIC) was established only for E. faecalis (LL-37, 57μM). Considering cytotoxicity, clavanin MO was able to reduce cell viability in many groups and demonstrated lowest LC₅₀. The Ca(OH)₂ up-regulated the production of MCP-1, TNF-α, IL-12 and IL-6 and down-regulated IL-1α, IL-10 and NO. Clavanins up-regulated the TNF-α and NO and down-regulated IL-10 production. LL-37 demonstrated up-regulation of IL-6 and TNF-α production and down-regulation in IL-10 and NO production. In conclusion, LL-37 demonstrated better antibacterial potential. In addition, Ca(OH)₂ demonstrated a proinflammatory response, while the HDPs modulated the inflammatory response from non-interference with the active cytokines in the osteoclastogenesis process, probably promoting the health of periradicular tissues.

Tazarotene as alternative topical treatment for onychomycosis

Background

Distal and lateral onychomycoses are the most frequent forms of onychomycosis, causing subungual hyperkeratosis that usually limits local penetration of antimycotic drugs. Tazarotene exerts anti-inflammatory and immune-modulating activities toward both infective agents and damaged keratinocytes. Given the well-documented efficacy of tazarotene on hyperkeratotic nail psoriasis, we investigated its therapeutic use in onychomycosis.

Patients and methods

We designed a preliminary open clinical trial in patients affected by distal and lateral subungual onychomycosis of the toenails and verified the fungistatic activity of tazarotene in vitro. Fifteen patients were treated with topical tazarotene 0.1% gel once per day for 12 weeks. Mycological cultures and potassium hydroxide stains of nail samples were performed at the beginning and at the end of the study. Treatment was considered effective when clinical healing and negative mycological culture were obtained. Onycholysis, nail bed discoloration, and subungual hyperkeratosis were measured using standardized methodologies and analyzed by means of Mann–Whitney test and analysis of variance. Fungistatic activity of tazarotene was evaluated by disk diffusion assay.

Results

Six patients (40%) reached a mycological cure on target nail samples already after 4 weeks of treatment. Complete clinical healing and negative cultures were reached in all patients at week 12, with a significant improvement of all clinical parameters of the infected nails. Disk diffusion assay after 48 hours of incubation with tazarotene solution showed a central area of inhibition in all examined fungal cultures.

Conclusion

Our results documented a good clinical outcome using topical tazarotene 0.1% gel in distal and lateral subungual onychomycosis and its fungistatic activity of tazarotene in vitro. The majority of patients appeared cured at a 6-month follow-up. The efficacy and safety of tazarotene must be confirmed on a larger number of patients, although already documented in nail psoriasis patients often affected by onychomycosis.

The prevalence of onychomycosis in psoriatic patients: a systematic review

We systematically reviewed all available literature concerning the prevalence of onychomycosis in patients with nail psoriasis and the distribution of pathogens causing onychomycosis in this specific group of patients. Databases searched were Pubmed, EMBASE and the Cochrane Controlled Clinical Trial Register. All studies reporting on the prevalence of onychomycosis in nail psoriasis were obtained, and quality assessment was determined by the STrengthening the Reporting of OBservational studies in Epidemiology checklist. Literature search revealed 720 studies, of which 10 studies met the inclusion criteria. The major limitation of the review was the heterogeneity of the included studies, which prevented the possibility to conduct a meta analysis. However, the average prevalence of 18.0% of onychomycosis in psoriatic patients seems to be increased when compared with control groups and literature on healthy population, even though the ultimate evidence remains lacking. As in the literature hypothesized shift in causative agents from dermatophytes to yeasts and/or moulds could not be confirmed. The clinical consequence of the relatively high prevalence of onychomycosis in psoriasis may be a general advice to rule out onychomycosis or concomitant onychomycosis in these patients with (suspected) nail psoriasis. This advice is stressed by the relative simplicity of treating the contribution of onychomycosis in the nail dystrophy but also the fact that nail psoriasis mostly is treated by immunosuppressive drugs, like steroids, methotrexate or biologics which may aggravate mycotic nail infections.

Adsorption of antimicrobial indolicidin-derived peptides on hydrophobic surfaces

The hydrophobic interaction between antimicrobial peptides and membrane hydrophobic cores is usually related to their cytotoxicity. In this study, the adsorption mechanism of five plasma membrane-associated peptides, indolicidin (IL) and its four derivatives, with hydrophobic ligands was investigated to understand the relationship between peptide hydrophobicity and bioactivity. The hydrophobic adsorption mechanisms of IL and its derivatives were interpreted thermodynamically and kinetically by reversed-phase chromatography (RPC) analysis and surface plasmon resonance (SPR) measurement, respectively. IL and its derivatives possess a similar random coil structure in both aqueous and organic solvents. Thermodynamic analysis showed that the binding enthalpy of peptides with higher electropositivity was lower than those with lower electropositivity and exhibited unfavorable binding entropy. Higher electropositivity peptides adsorbed to the hydrophobic surface arising from the less bound solvent on the peptide surface. A comparison with the kinetic analysis showed that IL and its derivatives adopt a two-state binding model (i.e., adsorption onto and self-association on the hydrophobic acyl chain) to associate with the hydrophobic surface, and the binding affinity of peptide self-association correlates well with peptide hemolysis. Consequently, this study provided a novel concept for understanding the action of plasma membrane-associated peptides.

Nail biology and nail science

The nail plate is the permanent product of the nail matrix. Its normal appearance and growth depend on the integrity of several components: the surrounding tissues or perionychium and the bony phalanx that are contributing to the nail apparatus or nail unit. The nail is inserted proximally in an invagination practically parallel to the upper surface of the skin and laterally in the lateral nail grooves. This pocket-like invagination has a roof, the proximal nail fold and a floor, the matrix from which the nail is derived. The germinal matrix forms the bulk of the nail plate. The proximal element forms the superficial third of the nail whereas the distal element provides its inferior two-thirds. The ventral surface of the proximal nail fold adheres closely to the nail for a short distance and forms a gradually desquamating tissue, the cuticle, made of the stratum corneum of both the dorsal and the ventral side of the proximal nail fold. The cuticle seals and therefore protects the ungual cul-de-sac. The nail plate is bordered by the proximal nail fold which is continuous with the similarly structured lateral nail fold on each side. The nail bed extends from the lunula to the hyponychium. It presents with parallel longitudinal rete ridges. This area, by contrast to the matrix has a firm attachment to the nail plate and nail avulsion produces a denudation of the nail bed. Colourless, but translucent, the highly vascular connective tissue containing glomus organs transmits a pink colour through the nail. Among its multiple functions, the nail provides counterpressure to the pulp that is essential to the tactile sensation involving the fingers and to the prevention of the hypertrophy of the distal wall tissue, produced after nail loss of the great toe nail.

Candidal onychomycosis: a mini-review

Onychomycosis is a common fungal infection affecting nails. The primary cause for onychomycosis is dermatophytes, while Candida species have emerged as second-line pathogens. Onychomycosis due to Candida (candidal onychomycosis) is increasingly found in individuals having defective immunity consequential to aging, diabetes mellitus, vascular diseases, HIV infection and drug therapies such as immunosuppressives and broad-spectrum antibiotics. Breached local immunity at the nail complex due to trauma, chronic exposure to moisture and chemicals including smoke, detergents, soap, etc., also contribute to candidal onychomycosis. Adhesion, filamentation, secretion of extracellular enzymes and the development of antifungal resistance are some of the virulence mechanisms of Candida species associated with onychomycosis. Diagnosis of onychomycosis depends on history and clinical examination, direct microscopic investigation, mycological culture and histopathology. Restoration of immune defenses, elimination of fungi using appropriate drug therapy and improvement of nail hygiene with the removal of predisposing factors are key aspects in the management of candidal onychomycosis.

Antimicrobial peptides, skin infections, and atopic dermatitis

The innate immune system evolved more than 2 billion years ago to first recognize pathogens then eradicate them. Several distinct defects in this ancient but rapidly responsive element of human immune defense account for the increased incidence of skin infections in atopics. These defects include abnormalities in the physical barrier of the epidermis, alterations in microbial pattern recognition receptors such as toll receptors and nucleotide binding oligomerization domains, and a diminished capacity to increase the expression of antimicrobial peptides during inflammation. Several antimicrobial peptides are affected including; cathelicidin, HBD-2, and HBD-3, which are lower in lesional skin of atopics compared with other inflammatory skin diseases, and dermcidin, which is decreased in sweat. Other defects in the immune defense barrier of atopics include a relative deficiency in plasmacytoid dendritic cells. In the future, understanding the cause of these defects may allow therapeutic intervention to reduce the incidence of infection in atopic individuals and potentially decrease the severity of this disorder.

Methicillin-resistant Staphylococcus aureus colonization in children with atopic dermatitis

Children with atopic dermatitis are more frequently colonized with Staphylococcus aureus than children without atopic dermatitis. However, little epidemiological data exist regarding the prevalence of methicillin-resistant S. aureus among children with atopic dermatitis. Recent studies have revealed an increasing prevalence of community-associated methicillin-resistant S. aureus among patients presenting to hospitals with serious bacterial infections, particularly those with cutaneous and soft tissue infections. As many atopic dermatitis patients are treated empirically with antibiotics for secondary skin infections, an understanding of the epidemiology of bacterial colonization and superinfection is essential for directing proper treatment in the atopic patient population. This study investigates the prevalence of risk factors for community-associated, methicillin-resistant S. aureus colonization among pediatric atopic dermatitis patients encountered at an academic pediatric dermatology clinic. An observational cross-sectional study was conducted at the Children's Hospital of Philadelphia in which 54 patients previously diagnosed with atopic dermatitis were enrolled. A detailed patient questionnaire, a complete cutaneous examination, and an evaluation of eczema severity according to the Eczema Area and Severity Index were completed at the time of enrollment. Bacterial cultures from the skin and nares were obtained to determine the frequency of colonization with either methicillin-sensitive S. aureus or methicillin-resistant S. aureus. Although most atopic dermatitis patients studied were colonized with S. aureus (43/54 [80%]), methicillin-resistant S. aureus was isolated from only seven atopic dermatitis patients (7/43 [16%]). Patients colonized with S. aureus were more likely to be male, to have been previously hospitalized, to have used a topical calcineurin inhibitor in combination with a topical steroid, and less likely to have used topical antibiotics. Bivariable analysis, however, revealed that only previous hospitalization was independently associated with an increased risk of methicillin-resistant S. aureus colonization. We observed that 80% of atopic dermatitis patients were colonized with S. aureus, and that of these patients, 16% of colonized patients were colonized with a methicillin-resistant strain. Methicillin-resistant S. aureus colonization was found to be significantly associated with previous hospitalization. Evidence also indicates that topical calcineurin inhibitors used in conjunction with topical steroids is associated with increased S. aureus colonization, while topical antibiotic use appears to decrease S. aureus colonization.

Identification, characterization and expression of cathelicidin in the pouch young of tammar wallaby (Macropus eugenii)

Antimicrobial peptides, such as cathelicidin, are an evolutionarily old defense system. However they have more complex actions than just simply their antimicrobial effects, including immunoregulation and interaction with the adaptive immune system. In this study we have characterized several novel cathelicidin-like peptides from the tammar wallaby (Macropus eugenii). The tammar cathelicidin-like (MaeuCath) mRNA were isolated based on the conservation of the cathelin-like amino terminus. Mature MaeuCath peptides were positively charged with hydrophobic carboxyl tails, features that are fundamental for antimicrobial function. MaeuCath1 was induced in tammar leukocytes in response to pathogen-associated molecular patterns from both gram positive and negative bacteria. In addition, we also examined the expression of MaeuCath1 in the primary and secondary lymphoid organs of the tammar neonate throughout early pouch life. The results from this study demonstrate the importance that MaeuCath1 may play in innate defense of the marsupial young, especially in the mucosal organs. Such expression of antimicrobial peptides may form part of the immune strategies of marsupials for neonatal survival during their post-partum development.

Antimicrobial peptides in human skin disease

The skin continuously encounters microbial pathogens. To defend against this, cells of the epidermis and dermis have evolved several innate strategies to prevent infection. Antimicrobial peptides are one of the primary mechanisms used by the skin in the early stages of immune defense. In general, antimicrobial peptides have broad antibacterial activity against gram-positive and negative bacteria and also show antifungal and antiviral activity. The antimicrobial activity of most peptides occurs as a result of unique structural characteristics that enable them to disrupt the microbial membrane while leaving human cell membranes intact. However, antimicrobial peptides also act on host cells to stimulate cytokine production, cell migration, proliferation, maturation, and extracellular matrix synthesis. The production by human skin of antimicrobial peptides such as defensins and cathelicidins occurs constitutively but also greatly increases after infection, inflammation or injury. Some skin diseases show altered expression of antimicrobial peptides, partially explaining the pathophysiology of these diseases. Thus, current research suggests that understanding how antimicrobial peptides modify susceptibility to microbes, influence skin inflammation, and modify wound healing, provides greater insight into the pathophysiology of skin disorders and offers new therapeutic opportunities.

LL-37, the only human member of the cathelicidin family of antimicrobial peptides

Antimicrobial peptides and their precursor molecules form a central part of human and mammalian innate immunity. The underlying genes have been thoroughly investigated and compared for a considerable number of species, allowing for phylogenetic characterization. On the phenotypical side, an ever-increasing number of very varied and distinctive influences of antimicrobial peptides on the innate immune system are reported. The basic biophysical understanding of mammalian antimicrobial peptides, however, is still very limited. This is especially unsatisfactory since knowledge of structural properties will greatly help in the understanding of their immunomodulatory functions. The focus of this review article will be on LL-37, the only cathelicidin-derived antimicrobial peptide found in humans. LL-37 is a 37-residue, amphipathic, helical peptide found throughout the body and has been shown to exhibit a broad spectrum of antimicrobial activity. It is expressed in epithelial cells of the testis, skin, the gastrointestinal tract, and the respiratory tract, and in leukocytes such as monocytes, neutrophils, T cells, NK cells, and B cells. It has been found to have additional defensive roles such as regulating the inflammatory response and chemo-attracting cells of the adaptive immune system to wound or infection sites, binding and neutralizing LPS, and promoting re-epthelialization and wound closure. The article aims to report the known biophysical facts, with an emphasis on structural evidence, and to set them into relation with insights gained on phylogenetically related antimicrobial peptides in other species. The multitude of immuno-functional roles is only outlined. We believe that this review will aid the future work on the biophysical, biochemical and immunological investigations of this highly intriguing molecule.

Activity of the Triazole Antifungal R126638 as Assessed by Corneofungimetry

BACKGROUND

R126638 is a novel triazole exhibiting potent in vitro and in vivo antifungal activity against fungal pathogens including dermatophytes and yeasts.

OBJECTIVE

To determine the antifungal activity in time in the stratum corneum of healthy volunteers after oral intake of R126638 at a daily dose of 100 or 200 mg for 1 week.

METHOD

Sixteen male volunteers were randomly allocated to oral treatment with either 100 or 200 mg of R126638 once daily for 1 week. Five cyanoacrylate skin surface strippings (CSSS) were obtained from the forearm of each subject before drug intake at day 1. CSSS were also collected during treatment at day 2 (24 h after the first drug intake, before the second drug intake), at day 4 (before the fourth drug intake) and at day 7 (10 h after the last drug intake). The post-treatment lingering effect was assessed at day 10 (3 days after treatment) and at day 14 (7 days after treatment). The corneofungimetry bioassay was performed on these CSSS to assess the antifungal profile of R126638. Cells of different fungal species (Trichophyton rubrum, Trichophyton mentagrophytes, Microsporum canis, Candida albicans and Malassezia globosa) were deposited and cultured for 10 days on CSSS in a sterile and controlled environment. The extent of fungal growth on the stratum corneum was determined using computerized image analysis.

RESULTS

R126638 clearly reduced the growth of all tested fungal species. The onset of effects of R126638 was evidenced at day 4 when it reached statistical significance for 3 of 5 species. At day 7, significance was reached for 4 of 5 species. During the posttreatment period, R126638 remained effective for 4 of 5 species at day 10, and this activity persisted until day 14 for 2 of 5 species.

CONCLUSION

A broad spectrum antifungal activity was rapidly expressed in the stratum corneum after oral intake of R126638. The drug likely reached the upper layers of the stratum corneum by diffusion and persisted in this location for at least 7 days after treatment.

Immunology of the Human Nail Apparatus: The Nail Matrix Is a Site of Relative Immune Privilege

The nail apparatus is constantly exposed to environmental damage. It requires effective immune responses to combat infection, while avoiding the loss of nail production and regeneration by autoaggressive immunity. By immunohistology, we define here previously unknown characteristics of the normal human nail immune system (NIS). Compared with other regions of nail epithelium, human leukocyte antigen (HLA)-A/B/C expression is prominently down regulated on both keratinocytes and melanocytes of the proximal nail matrix (PNM), whereas HLA-G(+) is upregulated here. Together with the expression of macrophage migration inhibitory factor in PNM, this may serve to inhibit an natural killer (NK) cell attack on major histocompatibility complex (MHC) class Ia-negative PNM. PNM also displays strong immunoreactivity for potent, locally generated immunosuppressants such as transforming growth factor-beta1, alpha-melanocyte stimulating hormone, insulin-like growth factor-1, and adrenocorticotropic hormone, exhibits unusually few CD1a(+), CD4(+), or CD8(+), NK, and mast cells. Finally, MHC class II and CD 209 expression on CD1a(+) cells in and around the PNM is reduced, indicating diminished antigen-presenting capacity. Thus, the NIS strikingly differs from the skin immune system, but shows intriguing similarities to the hair follicle immune system, including the establishment of an area of relative immune privilege in the PNM. This nail immune privilege may offer a relative safeguard against autoimmunity. But, the localized intraepithelial defect of innate and adaptive immunity in the PNM revealed here also may impede effective anti-infection defense.

The nail under fungal siege in patients with type II diabetes mellitus

Few studies have examined the prevalence of onychomycosis among diabetic patients. Given the morbidity linked to onychomycosis, and the ever-growing size of the diabetic population, a better recognition of this nail infection is welcome. To revisit the relative prevalence of dermatophyte, yeast and non-dermatophytic mould onychomycoses in diabetic adults in a prospective study using combined histomycology and cultures. Toenail clippings were collected for 3 years in 190 type II diabetic patients (136 men and 54 women) and from an age- and gender-matched group of non-diabetic subjects. All sampled nails showed clinical alterations reminiscent of onychomycosis. Histomycology and cultures were performed on each sample to distinguish onychomycosis from non-infectious onychodystrophy. Compared to non-diabetic subjects with nail alterations, diabetics showed a higher proportion of onychomycosis relative to non-fungal onychodystrophy. Diabetic men suffered more frequently from onychomycosis and onychodystrophy than diabetic women. When considering the nature of the fungal pathogens, dermatophytes predominated largely over yeast and non-dermatophytic moulds, both in diabetic and non-diabetic patients. Diabetic patients, particularly men, are at increased risk of developing onychomycosis. The morbidity linked to this disorder, and its impact on the foot status in diabetic subjects merit to be better appreciated by clinicians.

Antimicrobial peptides

Antimicrobial peptides (AMPs) are small molecular weight proteins with broad spectrum antimicrobial activity against bacteria, viruses, and fungi. These evolutionarily conserved peptides are usually positively charged and have both a hydrophobic and hydrophilic side that enables the molecule to be soluble in aqueous environments yet also enter lipid-rich membranes. Once in a target microbial membrane, the peptide kills target cells through diverse mechanisms. Cathelicidins and defensins are major groups of epidermal AMPs. Decreased levels of these peptides have been noted for patients with atopic dermatitis and Kostmann's syndrome, a congenital neutropenia. In addition to important antimicrobial properties, growing evidence indicates that AMPs alter the host immune response through receptor-dependent interactions. AMPs have been shown to be important in such diverse functions as angiogenesis, wound healing, and chemotaxis. As our knowledge of AMP biology expands, the precise role and relevance of these peptides will be better elucidated.

Un nuevo enfoque sobre la epidemiología de las onicomicosis

Onychomycoses represent a group of nail affections caused by one or more fungi. Whether aging represents a risk factor for developing onychomycosis, remains a question. In the present work, we studied the variations in frequency and prevalence of onychomycoses and non-mycotic onychodystrophies according to age. Our results show that there is an increase in the frequency and prevalence of onychomycoses and non-mycotic onychodystrophies predominantly in patients over forty years of age.

New insights into the effect of amorolfine nail lacquer

Despite improvements in antifungal strategies, the outcome of treating onychomycoses often remains uncertain. Several factors account for treatment failure, of which the pharmacokinetics and pharmacodynamics of the antifungal are of importance. The taxonomic nature and ungual location of the fungus cannot be neglected, besides the type of nail and its growth rate. In addition, the biological cycle of the fungus and the metabolic activity of the pathogen likely play a marked influence in drug response. The presence of natural antimicrobial peptides in the nail is also probably a key feature controlling the cure rates. There are many outstanding publications that cover the full spectrum of the field. The purpose of this review is to put in perspective some facets of activity of the topical treatment using amorolfine nail laquer. The antifungal activity of the drug is likely less pronounced in onychomycosis than that expected from conventional in vitro studies. However, the nail laquer formulation should reduce the propensity to form antifungal-resistant spores and limit the risk of reinfection.