TLN-58, an Additional hCAP18 Processing Form, Found in the Lesion Vesicle of Palmoplantar Pustulosis in the Skin

A fluorescence imaging technique suggests that sweat leakage in the epidermis contributes to the pathomechanism of palmoplantar pustulosis

Sweat is an essential protection system for the body, but its failure can result in pathologic conditions, including several skin diseases, such as palmoplantar pustulosis (PPP). As reduced intraepidermal E-cadherin expression in skin lesions was confirmed in PPP skin lesions, a role for interleukin (IL)-1-rich sweat in PPP has been proposed, and IL-1 has been implicated in the altered E-cadherin expression observed in both cultured keratinocytes and mice epidermis. For further investigation, live imaging of sweat perspiration on a mouse toe-pad under two-photon excitation microscopy was performed using a novel fluorescent dye cocktail (which we named JSAC). Finally, intraepidermal vesicle formation which is the main cause of PPP pathogenesis was successfully induced using our "LASER-snipe" technique with JSAC. "LASER-snipe" is a type of laser ablation technique that uses two-photon absorption of fluorescent material to destroy a few acrosyringium cells at a pinpoint location in three-dimensional space of living tissue to cause eccrine sweat leakage. These observatory techniques and this mouse model may be useful not only in live imaging for physiological phenomena in vivo such as PPP pathomechanism investigation, but also for the field of functional physiological morphology.

Peptide Stability Is Important but Not a General Requirement for Antimicrobial and Antibiofilm Activity In Vitro and In Vivo

Peptide stability to proteases has been a major requirement for developing peptide therapeutics. This study investigates the effects of peptide stability on antimicrobial and antibiofilm activity under various conditions. For this purpose, two human cathelicidin-derived peptides differing in stability to proteases were utilized. While GF-17, a peptide derived from the major antimicrobial region of human LL-37, can be rapidly cleaved by proteases, the engineered peptide 17BIPHE2 is resistant to multiple proteases. In the standard antimicrobial susceptibility, killing kinetics, and membrane permeabilization assays conducted in vitro using planktonic bacteria, these two peptides displayed similar potency. The two peptides were also similarly active against methicillin-resistant Staphylococcus aureus (MRSA) USA300 prior to biofilm formation. However, 17BIPHE2 was superior to GF-17 in disrupting preformed biofilms probably due to both enhanced stability and slightly higher DNA binding capacity. In a wax moth model, 17BIPHE2 better protected insects from MRSA infection-caused death than GF-17, consistent with the slower degradation of 17BIPHE2 than GF-17. Here, peptide antimicrobial activity was found to be critical for in vivo efficacy. When incorporated in the nanofiber/microneedle delivery device, GF-17 and 17BIPHE2 displayed a similar effect in eliminating MRSA in murine chronic wounds, underscoring the advantage of nanofibers in protecting the peptide from degradation. Since nanoformulation can ease the requirement of peptide stability, it opens the door to a direct use of natural peptides or their cocktails for antimicrobial treatment, accelerating the search of effective antibiofilm peptides to treat chronic wounds.

Alternative Antibiotics in Dentistry: Antimicrobial Peptides

The rise of antibiotic resistant bacteria due to overuse and misuse of antibiotics in medicine and dentistry is a growing concern. New approaches are needed to combat antibiotic resistant (AR) bacterial infections. There are a number of methods available and in development to address AR infections. Dentists conventionally use chemicals such as chlorohexidine and calcium hydroxide to kill oral bacteria, with many groups recently developing more biocompatible antimicrobial peptides (AMPs) for use in the oral cavity. AMPs are promising candidates in the treatment of (oral) infections. Also known as host defense peptides, AMPs have been isolated from animals across all kingdoms of life and play an integral role in the innate immunity of both prokaryotic and eukaryotic organisms by responding to pathogens. Despite progress over the last four decades, there are only a few AMPs approved for clinical use. This review summarizes an Introduction to Oral Microbiome and Oral Infections, Traditional Antibiotics and Alternatives & Antimicrobial Peptides. There is a focus on cationic AMP characteristics and mechanisms of actions, and an overview of animal-derived natural and synthetic AMPs, as well as observed microbial resistance.

Cathelicidin LL-37 in Health and Diseases of the Oral Cavity

The mechanisms for maintaining oral cavity homeostasis are subject to the constant influence of many environmental factors, including various chemicals and microorganisms. Most of them act directly on the oral mucosa, which is the mechanical and immune barrier of the oral cavity, and such interaction might lead to the development of various oral pathologies and systemic diseases. Two important players in maintaining oral health or developing oral pathology are the oral microbiota and various immune molecules that are involved in controlling its quantitative and qualitative composition. The LL-37 peptide is an important molecule that upon release from human cathelicidin (hCAP-18) can directly perform antimicrobial action after insertion into surface structures of microorganisms and immunomodulatory function as an agonist of different cell membrane receptors. Oral LL-37 expression is an important factor in oral homeostasis that maintains the physiological microbiota but is also involved in the development of oral dysbiosis, infectious diseases (including viral, bacterial, and fungal infections), autoimmune diseases, and oral carcinomas. This peptide has also been proposed as a marker of inflammation severity and treatment outcome.

Severe de novo pustular psoriasiform immune-related adverse event associated with nivolumab treatment for metastatic esophageal adenocarcinoma

Breakthrough targeted therapies have produced significant improvements in survival for cancer patients, but have a propensity to cause cutaneous immune-related adverse events (irAEs). Psoriasiform irAEs, representing about 4% of dermatologic toxicities associated with immune checkpoint inhibitor (ICI) therapy, are usually mild, occur in older patients and present as an exacerbation of existing psoriasis after several doses of ICI therapy. We report a case of a 58-year-old woman with metastatic esophageal adenocarcinoma and no prior history of psoriasis who developed a pustular psoriasiform irAE, beginning 3 days after initiation of nivolumab and progressing to confluent erythroderma with pustules over 2 weeks despite topical steroid use. She had concurrent acrodermatitis enteropathica, clinically diagnosed and confirmed with a low serum zinc level, that improved with supplementation. Her psoriasiform irAE was refractory to systemic steroids and acitretin, prompting discontinuation of nivolumab and treatment with ustekinumab and concomitant slow taper of acitretin and prednisone. Pustular psoriasiform irAE is a rare but severe dermatologic toxicity resulting from ICI therapy. Given the diverse morphologic types of cutaneous irAEs that can occur during ICI therapy, a clinical and histopathologic examination of dermatologic toxicities is critical to identify patients who may benefit from biologic therapy.

A Randomized, Double-Blind, Placebo-Controlled, Phase 2a Study to Evaluate the Efficacy and Safety of RIST4721 in Subjects with Palmoplantar Pustulosis

Introduction

Palmoplantar pustulosis (PPP) is a chronic inflammatory skin condition with neutrophilic infiltration of the epidermis. RIST4721 antagonizes CXC chemokine receptor type 2, which is important in neutrophil recruitment and migration. In this study, the efficacy and safety of RIST4721 versus placebo were assessed in adult subjects with moderate to severe PPP.

Methods

This phase 2a, multicenter, randomized, double-blind, placebo-controlled study investigated RIST4721 versus placebo in subjects with moderate to severe PPP. Key eligibility criteria included: Palmoplantar Pustulosis Area and Severity Index (PPPASI) ≥ 8 and Palmoplantar Pustulosis Physician Global Assessment ≥ 3. Subjects were randomized 1:1 to RIST4721 300 mg or placebo once daily for 28 days. The primary efficacy endpoints were relative change from baseline in fresh and total pustule count at day 28.

Results

Fifteen subjects received RIST4721 and 19 subjects received placebo. Treatment with RIST4721 was found to be generally well tolerated. At day 28, the mean ± standard deviation (SD) relative change from baseline in fresh pustule count was 0.86 ± 0.692 and 0.53 ± 0.561 (P = 0.240) and in total pustule count was 0.99 ± 0.667 and 0.96 ± 0.672 (P = 0.804) for RIST4721 and placebo groups, respectively. Subgroup analysis of subjects with progressing disease demonstrated that subjects with a PPPASI-50 at day 28 was significantly higher for subjects treated with RIST4721 (71%) than placebo (15%) (P = 0.022).

Conclusion

Preliminary data suggest RIST4721 is well tolerated and may be a potential therapy for patients with PPP.

Trial Registration

RIST4721-201 was registered in June 2019 at clinicaltrials.gov: NCT03988335.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13555-021-00632-7.

Spotlight on the Selected New Antimicrobial Innate Immune Peptides Discovered During 2015-2019

BACKGROUND

Antibiotic resistance is a global issue and new anti-microbials are required.

INTRODUCTION

Anti-microbial peptides are important players of host innate immune systems that prevent infections. Due to their ability to eliminate drug-resistant pathogens, AMPs are promising candidates for developing the next generation of anti-microbials.

METHODS

The anti-microbial peptide database provides a useful tool for searching, predicting, and designing new AMPs. In the period from 2015-2019, ~500 new natural peptides have been registered.

RESULTS

This article highlights a selected set of new AMP members with interesting properties. Teixobactin is a cell wall inhibiting peptide antibiotic, while darobactin inhibits a chaperone and translocator for outer membrane proteins. Remarkably, cOB1, a sex pheromone from commensal enterococci, restricts the growth of multidrug-resistant Enterococcus faecalis in the gut at a picomolar concentration. A novel proline-rich AMP has been found in the plant Brassica napus. A shrimp peptide MjPen- II comprises three different sequence domains: serine-rich, proline-rich, and cysteine-rich regions. Surprisingly, an amphibian peptide urumin specifically inhibits H1 hemagglutinin-bearing influenza A virus. Defensins are abundant and typically consist of three pairs of intramolecular disulfide bonds. However, rat rattusin dimerizes via forming five pairs of intermolecular disulfide bonds. While human LL-37 can be induced by vitamin D, vitamin A induces the expression of resistin-like molecule alpha (RELMα) in mice. The isolation and characterization of an alternative human cathelicidin peptide, TLN-58, substantiates the concept of one gene multiple peptides. The involvement of a fly AMP nemuri in sleep induction may promote the research on the relationship between sleep and infection control.

CONCLUSION

The functional roles of AMPs continue to grow and the general term "innate immune peptides" becomes useful. These discoveries widen our view on the anti-microbial peptides and may open new opportunities for developing novel peptide therapeutics for different applications.

Short and Robust Anti-Infective Lipopeptides Engineered Based on the Minimal Antimicrobial Peptide KR12 of Human LL-37

This study aims to push the frontier of the engineering of human cathelicidin LL-37, a critical antimicrobial innate immune peptide that wards off invading pathogens. By sequential truncation of the smallest antibacterial peptide (KR12) of LL-37 and conjugation with fatty acids, with varying chain lengths, a library of lipopeptides is generated. These peptides are subjected to antibacterial activity and hemolytic assays. Candidates (including both forms made of l- and d-amino acids) with the optimal cell selectivity are subsequently fed to the second layer of in vitro filters, including salts, pH, serum, and media. These practices lead to the identification of a miniature LL-37 like peptide (d-form) with selectivity, stability, and robust antimicrobial activity in vitro against both Gram-positive and negative bacteria. Proteomic studies reveal far fewer serum proteins that bind to the d-form than the l-form peptide. C10-KR8d targets bacterial membranes to become helical, making it difficult for bacteria to develop resistance in a multiple passage experiment. In vivo, C10-KR8d is able to reduce bacterial burden of methicillin-resistant Staphylococcus aureus (MRSA) USA300 LAC in neutropenic mice. In addition, this designer peptide prevents bacterial biofilm formation in a catheter-associated mouse model. Meanwhile, C10-KR8d also recruits cytokines to the vicinity of catheters to clear infection. Thus, based on the antimicrobial region of LL-37, this study succeeds in identifying the smallest anti-infective peptide C10-KR8d with both robust antimicrobial, antibiofilm, and immune modulation activities.

Cigarette Smoke Underlies the Pathogenesis of Palmoplantar Pustulosis via an IL-17A-Induced Production of IL-36γ in Tonsillar Epithelial Cells

Palmoplantar pustulosis (PPP) is characterized by sterile pustules on the palms and soles. A strong association between PPP and tobacco smoking has been reported, and it has been speculated that the IL-17A pathway may play an important role in PPP. Recent studies have suggested that IL-36 plays a pivotal role in the pathogenesis of psoriasis and its subtypes. The relationships among IL-36, smoking, and PPP have not been examined. Here, we investigated the relationships among the smoking index, severity of the clinical condition of PPP, and in vitro dynamics of IL-36 in human tonsillar epithelial cells under the condition of exposure to a cigarette smoke extract. The results demonstrated that the Palmoplantar Pustulosis Area and Severity Index was strongly and positively correlated with the smoking index in female patients. Immunohistochemical examinations showed that IL-36γ was highly expressed in tonsillar epithelial cells from patients with PPP but not in those from patients with recurrent tonsillitis without PPP. The in vitro study revealed that IL-17A synergistically induced a release of IL-36γ under cigarette smoke extract exposure. These results suggest that local production of IL-36γ by epithelial cells induced by cigarette smoke exposure plays an important role in the pathogenesis of PPP.

High-quality Fluorescence Imaging of the Human Acrosyringium Using a Transparency: Enhancing Technique and an Improved, Fluorescent Solvatochromic Pyrene Probe

Two-photon, excitation fluorescent microscopy featuring autofluorescence or immunofluorescence, combined with optical clearance using a transparency-enhancing technique, allows deep imaging of three-dimensional (3D) skin structures. However, it remains difficult to obtain high-quality images of individual cells or 3D structures. We combined a new dye with a transparency-enhancing technology and performed high-quality structural analysis of human epidermal structures, especially the acrosyringium. Human fingertip skin samples were collected, formalin-fixed, embedded in both frozen and paraffin blocks, sliced, stained with propidium iodide, optically cleared using a transparency-enhancing technique, and stained with a new fluorescent, solvatochromic pyrene probe. Microscopy revealed fine skin features and detailed epidermal structures including the stratum corneum (horny layer), keratinocytes, eccrine sweat glands, and peripheral nerves. Three-dimensional reconstruction of an entire acrosyringium was possible in one sample. This new fluorescence microscopy technique yields high-quality epidermal images and will aid in histopathological analyses of skin disorders.

Cathelicidin represents a new target for manipulation of skin inflammation in Netherton syndrome

Netherton syndrome (NS) is a severe ichthyosis caused by inactivating mutations in the SPINK5 gene encoding the serine protease inhibitor LEKTI. Spink5^-/- mice recapitulate NS and die perinatally from extensive dehydration as a result of a severe defect of the epidermal barrier. We showed that deletion of Klk5 in Spink5^-/- rescues neonatal lethality (Furio et al., 2015). However, Spink5^-/-Klk5^-/- mice developed skin shedding and inflammation during the first week from birth and the majority (70%) succumbed on P7. The remaining mice lived short (i.e. mean survival was 5 months) indicating alternative inflammatory pathways. Since cathelicidin is increased in Spink5^-/- epidermis, we investigated whether it could be implicated in NS pathology. Ablation of Camp in Spink5^-/- suppressed epidermal inflammation and restored abnormal epidermal differentiation, nevertheless, it failed to inhibit overdesquamation and Spink5^-/-Camp^-/- succumbed perinatally due to skin barrier defect, similarly to Spink5^-/-. Joint invalidation of Klk5 and Camp significantly extended survival of Spink5^-/-Klk5^-/-Camp^-/- mice. We provide evidence that cathelicidin is implicated in NS-associated skin inflammation in vivo. Therefore, marketed products that are known to reduce cathelicidin expression could be repurposed for the management of NS.

Guselkumab for the treatment of palmoplantar pustulosis

INTRODUCTION

Palmoplantar pustulosis, or pustulosis palmaris et plantaris (PPP), is a chronic, recurrent inflammatory skin disease that is sometimes unresponsive to conventional therapy. The anti-interleukin 23 antibody guselkumab is effective for treating PPP.

AREAS COVERED

This review details the current understanding of PPP and discusses why guselkumab may be effective. Guselkumab is only approved for the treatment of PPP in Japan. In the United States, Canada, the European Union, and several other countries, it is approved for the treatment of moderate-to-severe plaque psoriasis, but not for PPP. Furthermore, guselkumab was approved only 1 year ago; its efficacy will be proven only by phase 2 and 3 clinical trials.

EXPERT OPINION

The first double-blinded randomized placebo-controlled trial (RCT) of guselkumab for PPP has been completed. The drug was effective, and guselkumab could be used as a new agent for PPP treatment, in addition to several conventional therapeutics. However, several issues remain. For example, there is no mouse model of PPP, so careful observation of human PPP patients and establishment of a good experimental PPP model are essential.

Palmoplantar pustulosis: Current understanding of disease definition and pathomechanism

Pustulosis palmaris et plantaris, or palmoplantar pustulosis (PPP), is a chronic pustular dermatitis involving the palms and soles and is characterized by vesicles, pustules, erythema, lichenification, and abnormal desquamation. It is one of the most common skin diseases in Japan but its pathomechanism is unclear and the disease remains poorly defined. Consequently, adequate treatment for PPP is lacking. As a localized type of pustular psoriasis, PPP has long been treated with the conventional therapies used for plaque-type psoriasis, especially in Western countries. However, PPP may be a distinct entity, with a much lower prevalence in Western countries than in Japan. Furthermore, while treatment has yielded insights into the underlying pathology in plaque-type psoriasis, the pathogenesis of PPP has yet to be elucidated. In 2018, Gulselkumab, a monoclonal antibody against interleukin (IL)-23, was certified for use in Japan and is the first biologic effective in PPP both in Japanese and other patients. In this review, we summarize the current understanding of PPP, including the revised definition and possible pathomechanism. The information presented herein provides a more complete picture of PPP and may facilitate the development of improved treatment options.

Expression and Function of Host Defense Peptides at Inflammation Sites

There is a growing interest in the complex role of host defense peptides (HDPs) in the pathophysiology of several immune-mediated inflammatory diseases. The physicochemical properties and selective interaction of HDPs with various receptors define their immunomodulatory effects. However, it is quite challenging to understand their function because some HDPs play opposing pro-inflammatory and anti-inflammatory roles, depending on their expression level within the site of inflammation. While it is known that HDPs maintain constitutive host protection against invading microorganisms, the inducible nature of HDPs in various cells and tissues is an important aspect of the molecular events of inflammation. This review outlines the biological functions and emerging roles of HDPs in different inflammatory conditions. We further discuss the current data on the clinical relevance of impaired HDPs expression in inflammation and selected diseases.

Modulation of antimicrobial potency of human cathelicidin peptides against the ESKAPE pathogens and in vivo efficacy in a murine catheter-associated biofilm model

Antimicrobial peptides are essential components of innate immune systems that protect hosts from infection. They are also useful candidates for developing a new generation of antibiotics to fight antibiotic-resistant pathogens. Human innate immune peptide LL-37 can inhibit biofilm formation, but suffers from high cost due to a long peptide length and rapid protease degradation. To improve the peptide, we previously identified the major active region and changed the peptide backbone structure. This study designed two families of new peptides by altering peptide side chains. Interestingly, these peptides displayed differential potency against various ESKAPE pathogens in vitro and substantially reduced hemolysis. Further potency test in vivo revealed that 17tF-W eliminated the burden of methicillin-resistant Staphylococcus aureus (MRSA) USA300 in both mouse-embedded catheters and their surrounding tissues. In addition, peptide treatment suppressed the level of chemokine TNFα, and boosted the levels of chemokines MCP-1, IL-17A and IL-10 in the surrounding tissues of the infected catheter embedded in mice. In conclusion, we have designed a set of new LL-37 peptides with varying antimicrobial activities, opening the door to potential topical treatment of infections involving different drug-resistant pathogens.

Design of Antimicrobial Peptides: Progress Made with Human Cathelicidin LL-37

The incorporation of the innate immune system into humans is essential for survival and health due to the rapid replication of invading microbes and the delayed action of the adaptive immune system. Antimicrobial peptides are important components of human innate immunity. Over 100 such peptides have been identified in various human tissues. Human cathelicidin LL-37 is best studied, and there has been a growing interest in designing new peptides based on LL-37. This chapter describes the alternative processing of the human cathelicidin precursor, protease digestion, and lab cutting of LL-37. Both a synthetic peptide library and structure-based design are utilized to identify the active regions. Although challenging, the determination of the 3D structure of LL-37 enabled the identification of the core antimicrobial region. The minimal region of LL-37 can be function-dependent. We discuss the design and potential applications of LL-37 into antibacterial, antibiofilm, antiviral, antifungal, immune modulating, and anticancer peptides. LL-37 has been engineered into 17BIPHE2, a stable, selective, and potent antimicrobial, antibiofilm, and anticancer peptide. Both 17BIPHE2 and SAAP-148 can eliminate the ESKAPE pathogens and show topical in vivo antibiofilm efficacy. Also discussed are other application strategies, including peptide formulation, antimicrobial implants, and peptide-inducing factors such as vitamin D and sunlight. Finally, we summarize what we learned from peptide design based on human LL-37.

Bioinspired Designs, Molecular Premise and Tools for Evaluating the Ecological Importance of Antimicrobial Peptides

This review article provides an overview of recent developments in antimicrobial peptides (AMPs), summarizing structural diversity, potential new applications, activity targets and microbial killing responses in general. The use of artificial and natural AMPs as templates for rational design of peptidomimetics are also discussed and some strategies are put forward to curtail cytotoxic effects against eukaryotic cells. Considering the heat-resistant nature, chemical and proteolytic stability of AMPs, we attempt to summarize their molecular targets, examine how these macromolecules may contribute to potential environmental risks vis-à-vis the activities of the peptides. We further point out the evolutional characteristics of the macromolecules and indicate how they can be useful in designing target-specific peptides. Methods are suggested that may help to assess toxic mechanisms of AMPs and possible solutions are discussed to promote the development and application of AMPs in medicine. Even if there is wide exposure to the environment like in the hospital settings, AMPs may instead contribute to prevent healthcare-associated infections so long as ecotoxicological aspects are considered.