Antimicrobial peptides: old molecules with new ideas

Transformation of human cathelicidin LL-37 into selective, stable, and potent antimicrobial compounds

This Letter reports a family of novel antimicrobial compounds obtained by combining peptide library screening with structure-based design. Library screening led to the identification of a human LL-37 peptide resistant to chymotrypsin. This d-amino-acid-containing peptide template was active against Escherichia coli but not methicillin-resistant Staphylococcus aureus (MRSA). It possesses a unique nonclassic amphipathic structure with hydrophobic defects. By repairing the hydrophobic defects, the peptide (17BIPHE2) gained activity against the ESKAPE pathogens, including Enterococcus faecium, S. aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa, and Enterobacter species. In vitro, 17BIPHE2 could disrupt bacterial membranes and bind to DNA. In vivo, the peptide prevented staphylococcal biofilm formation in a mouse model of catheter-associated infection. Meanwhile, it boosted the innate immune response to further combat the infection. Because these peptides are potent, cell-selective, and stable to several proteases, they may be utilized to combat one or more ESKAPE pathogens.

Classification of inflammatory skin diseases: a proposal based on the disorders of the three-layered defense systems, barrier, innate immunity and acquired immunity

The host defense system of the skin is composed of (1) a barrier, (2) innate immunity, and (3) acquired immunity. Inflammatory skin diseases can be classified into one of the disorders of these layers of the defense system, unless there is an ordinary response to specific infectious agents or internal/external injury. Any inflammatory skin disease partly simulates the response to real infections or dangers. Disorders of acquired immunity can be classified into (1) immunodeficiency, (2) immunohyperactivity (allergy), and (3) qualitative disorder (autoimmunity). Disorders of innate immunity can be classified into (1) innate immunodeficiency, (2) innate immunohyperactivity (general or local autoinflammation), and (3) qualitative disorder (general or local innate autoimmunity). The barrier of the skin is composed of (1) the physical barrier and (2) the chemical barrier. Several diseases, such as atopic dermatitis, are attributed to the disorder of these components of the barrier. Here, we propose an algorithm to classify the pathology of inflammatory skin diseases by means of what disorder in the specific layer of the host defense system is truly responsible.

The antimicrobial peptide lysozyme is induced after multiple trauma

The antimicrobial peptide lysozyme is an important factor of innate immunity and exerts high potential of antibacterial activity. In the present study we evaluated the lysozyme expression in serum of multiple injured patients and subsequently analyzed their possible sources and signaling pathways. Expression of lysozyme was examined in blood samples of multiple trauma patients from the day of trauma until 14 days after trauma by ELISA. To investigate major sources of lysozyme, its expression and regulation in serum samples, different blood cells, and tissue samples were analysed by ELISA and real-time PCR. Neutrophils and hepatocytes were stimulated with cytokines and supernatant of Staphylococcus aureus. The present study demonstrates the induction and release of lysozyme in serum of multiple injured patients. The highest lysozyme expression of all tested cells and tissues was detected in neutrophils. Stimulation with trauma-related factors such as interleukin-6 and S. aureus induced lysozyme expression. Liver tissue samples of patients without trauma show little lysozyme expression compared to neutrophils. After stimulation with bacterial fragments, lysozyme expression of hepatocytes is upregulated significantly. Toll-like receptor 2, a classic receptor of Gram-positive bacterial protein, was detected as a possible target for lysozyme induction.

Isotretinoin therapy changes the expression of antimicrobial peptides in acne vulgaris

In acne vulgaris, antimicrobial peptides (AMPs) could play a dual role; i.e., protective by acting against Propionibacterium acnes, pro-inflammatory by acting as signalling molecules. The cutaneous expression of 15 different AMPs was investigated in acne patients; furthermore, the impact of isotretinoin therapy on AMP expression was analysed in skin biopsies from 13 patients with acne vulgaris taken before, during and after a 6-month treatment cycle with isotretinoin using quantitative real-time polymerase chain reaction. Cutaneous expression of the AMPs cathelicidin, human β-defensin-2 (HBD-2), lactoferrin, lysozyme, psoriasin (S100A7), koebnerisin (S100A15), and RNase 7 was upregulated in untreated acne vulgaris, whereas α-defensin-1 (HNP-1) was downregulated compared to controls. While relative expression levels of cathelicidin, HBD-2, lactoferrin, psoriasin (S100A7), and koebnerisin (S100A15) decreased during isotretinoin treatment, only those of cathelicidin and koebnerisin returned to normal after 6 months of isotretinoin therapy. The increased expression of lysozyme and RNase 7 remained unaffected by isotretinoin treatment. The levels of granulysin, RANTES (CCL5), perforin, CXCL9, substance P, chromogranin B, and dermcidin were not regulated in untreated acne patients and isotretinoin had no effect on these AMPs. In conclusion, the expression of various AMPs is altered in acne vulgaris. Isotretinoin therapy normalizes the cutaneous production of distinct AMPs while the expression of others is still increased in healing acne. Considering the antimicrobial and pro-inflammatory role of AMPs, these molecules could serve as specific targets for acne therapy and maintenance of clinical remission.

The new insight into the role of antimicrobial proteins-alarmins in the immunopathogenesis of psoriasis

The pathognesis of psoriasis still remains not fully elucidated. Recent advances favor the idea that interactions between innate and adaptive immune response drive inflammatory process in this disease. Innate antimicrobial peptides and proteins (AMPs) are diverse group of small molecules that provide the first line of defense against invading pathogens. In recent years, the novel functions of AMPs have been identified. There are three subclasses among AMPs that have gained the special interest as a potentially important player in the pathogenesis of psoriasis: cathelicidin, S100 proteins, and defensins. These AMPs have been shown to modulate and trigger host immune response in psoriasis acting as interplayer between innate and adaptive immune mechanisms. Overexpressed in psoriatic lesions, they prime immune cells for enhanced production of proinflammatory mediators and act as chemoattractant for leukocytes. Therefore, the novel term describing AMPs alarmins has been suggested. As multifunctional player in pathogenesis of psoriasis, AMPs may constitute potential target for therapeutic interventions. However, further investigations are required to establish the methods of downregulation of the aberrant proinflammatory functions of AMPs without increasing the risk of infections.

Determination of disulfide linkages in antimicrobial peptides of the macin family by combination of top-down and bottom-up proteomics

Macins are a distinct class of antimicrobial peptides (AMPs) produced by leeches and Hydra. Their function depends strongly on their three-dimensional structure. In order to support structural elucidation of these AMPs, the knowledge and proper assignment of disulfide bonds formed in these cysteine-rich peptides is a prerequisite. In this report, we outline an analytical strategy, encompassing a combination of top-down MS based analytics and sequence-dependent enzyme cleavage under native conditions followed by high mass accuracy and high resolution MS/MS analysis by LTQ-Orbitrap MS to assign disulfide linkages of three members of the macin family, namely neuromacin, theromacin, and hydramacin-1. The results revealed that the eight cysteine residues conserved in all three macins form the same four disulfide bonds, i.e. [C1:C6], [C2:C5], [C3:C7], and [C4:C8]. Theromacin, which possess two additional cysteine residues, forms a fifth disulfide bond.

BIOLOGICAL SIGNIFICANCE

Beside the high biological significance which is based on the inherent dependence of biological activity on the structural features of antimicrobial peptides (which holds true for entirely every protein), the presented analytical strategy will be of wide interest, as it widens the available toolbox for the analysis of this important posttranslational modification.

Cationic Bioactive Peptide from the Seeds of Benincasa hispida

A designated bioactive peptide “Hispidalin” purified from the seeds of Benincasa hispida, which is a medicinal plant, belongs to Cucurbitaceae family. Purification was achieved by using a procedure consisting of extraction from potassium phosphate buffer followed by FPLC and HPLC steps. Based on amino acid residue, this peptide is amphipathic and basic with one net positive charge having isoelectric pH 8.1. This peptide is without sulphur containing amino acid suggesting its extended conformation lacking double bond secondary structure. The results obtained from MALDI-TOF suggested that Hispidalin is of molecular mass 5.7 KDa with 49 amino acid residues and confirmed SDS-PAGE resolved ∼6.0 KDa protein band. This novel and unknown peptide “Hispidalin” showed broad and potent inhibitory effects against various human bacterial and fungal pathogens; its growth inhibition was significantly comparable with commercial antibacterial and antifungal drugs. The Hispidalin at 40 μg/mL concentration exhibited 70.8% DPPH free radical-scavenging activity and 69.5% lipid peroxide inhibition. Thus, in the present study, Hispidalin demonstrated remarkable antimicrobial and antioxidant potentials from the seeds of B. hispida.

Nanoparticles as multifunctional devices for the topical treatment of cutaneous leishmaniasis

INTRODUCTION

Cutaneous and mucocutaneous leishmaniasis are major tropical skin diseases. Topical treatment is currently limited to the least severe forms of cutaneous leishmaniasis (CL) without risk of dissemination. It is also recommended in combination with systemic therapy for more severe forms. Progresses in this modality of treatment are hindered by the heterogeneity of the disease and shortcomings in the clinical trials.

AREAS COVERED

This review overlooks three major modalities of topical therapies in use or under investigation against CL: chemotherapy, photodynamic therapy and immunotherapy; either with older compounds such as paramomycin or more recent nitric oxide donors, antimicrobial peptides or silver derivatives. The advantages and limitations of their administration with newer formulation strategies such as nanoparticles (NPs) are discussed.

EXPERT OPINION

The efficacy of a topical treatment against CL depends not only on the intrinsic antileishmanial activity of the drug but also on the amount of drug available in the dermis. NPs as sustained release systems and permeation enhancers could favour the creation of a drug reservoir in the dermis. Additionally, certain NPs have immunomodulatory properties or wound healing capabilities of benefit in CL treatment. Pending task is the selective delivery of active compounds to intracellular amastigotes, because even small NPs are unable to penetrate deeply into the skin to encounter infected macrophages (except in ulcerative lesions).

S100A8-S100A9 protein complex mediates psoriasis by regulating the expression of complement factor C3

Psoriasis is a common heterogeneous inflammatory skin disease with a complex pathophysiology and limited treatment options. Here we performed proteomic analyses of human psoriatic epidermis and found S100A8-S100A9, also called calprotectin, as the most upregulated proteins, followed by the complement component C3. Both S100A8-S100A9 and C3 are specifically expressed in lesional psoriatic skin. S100A9 is shown here to function as a chromatin component modulating C3 expression in mouse and human cells by binding to a region upstream of the C3 start site. When S100A9 was genetically deleted in mouse models of skin inflammation, the psoriasis-like skin disease and inflammation were strongly attenuated, with a mild immune infiltrate and decreased amounts of C3. In addition, inhibition of C3 in the mouse model strongly reduced the inflammatory skin disease. Thus, S100A8-S100A9 can regulate C3 at the nuclear level and present potential new therapeutic targets for psoriasis.

Immunostimulation in the treatment for chronic fatigue syndrome/myalgic encephalomyelitis

Chronic fatigue syndrome (CFS)/myalgic encephalomyelitis (ME) has long been associated with the presence of infectious agents, but no single pathogen has been reliably identified in all patients with the disease. Recent studies using metagenomic techniques have demonstrated the presence of thousands of microbes in the human body that were previously undetected and unknown to science. More importantly, such species interact together by sharing genes and genetic function within communities. It follows that searching for a singular pathogen may greatly underestimate the microbial complexity potentially driving a complex disease like CFS/ME. Intracellular microbes alter the expression of human genes in order to facilitate their survival. We have put forth a model describing how multiple species-bacterial, viral, and fungal-can cumulatively dysregulate expression by the VDR nuclear receptor in order to survive and thus drive a disease process. Based on this model, we have developed an immunostimulatory therapy that is showing promise inducing both subjective and objective improvement in patients suffering from CFS/ME.

Antibiotic development challenges: the various mechanisms of action of antimicrobial peptides and of bacterial resistance

Antimicrobial peptides (AMPs) are natural antibiotics produced by various organisms such as mammals, arthropods, plants, and bacteria. In addition to antimicrobial activity, AMPs can induce chemokine production, accelerate angiogenesis, and wound healing and modulate apoptosis in multicellular organisms. Originally, their antimicrobial mechanism of action was thought to consist solely of an increase in pathogen cell membrane permeability, but it has already been shown that several AMPs do not modulate membrane permeability in the minimal lethal concentration. Instead, they exert their effects by inhibiting processes such as protein and cell wall synthesis, as well as enzyme activity, among others. Although resistance to these molecules is uncommon several pathogens developed different strategies to overcome AMPs killing such as surface modification, expression of efflux pumps, and secretion of proteases among others. This review describes the various mechanisms of action of AMPs and how pathogens evolve resistance to them.

Microbial ecology of the skin in the era of metagenomics and molecular microbiology

The skin is the primary physical barrier between the body and the external environment and is also a substrate for the colonization of numerous microbes. Previously, dermatological microbiology research was dominated by culture-based techniques, but significant advances in genomic technologies have enabled the development of less-biased, culture-independent approaches to characterize skin microbial communities. These molecular microbiology approaches illustrate the great diversity of microbiota colonizing the skin and highlight unique features such as site specificity, temporal dynamics, and interpersonal variation. Disruptions in skin commensal microbiota are associated with the progression of many dermatological diseases. A greater understanding of how skin microbes interact with each other and with their host, and how we can therapeutically manipulate those interactions, will provide powerful tools for treating and preventing dermatological disease.

Identification and characterization of defensin genes from the endoparasitoid wasp Cotesia vestalis (Hymenoptera: Braconidae)

Defensins are members of a large and diverse family of antimicrobial peptides (AMPs) containing three or four intramolecular disulfide bonds. They are widely distributed from vertebrates to invertebrates, and serve as critical defense molecules protecting the host from the invasion of pathogens or protozoan parasites. Cotesia vestalis is a small endoparasitoid wasp that lays eggs in larvae of Plutella xylostella, a cosmopolitan pest of cruciferous crops. We identified and characterized three full-length cDNAs encoding putative defensin-like peptides from C. vestalis, named CvDef1, CvDef2 and CvDef3. Phylogenetic analyses of these sequences showed that they are present in two clades, CITDs and PITDs, indicating a diversity of defensins in C. vestalis. We analyzed their expression patterns in larvae, pupae and adults by semi-quantitative RT-PCR. The results showed that CvDef1 mRNA was expressed from the end stage of the second instar larva, CvDef3 mRNA from the early stage of the second instar larva, and CvDef2 mRNA was expressed in all developmental stages of C. vestalis. Furthermore, CvDef1 showed antimicrobial activity against gram-positive and gram-negative bacteria. Growth kinetics of Staphylococcus aureus indicated that CvDef1 had much better antimicrobial ability than ampicillin, making it a potential candidate for practical use. Transmission electron microscopic (TEM) examination of CvDef1-treated S. aureus cells showed extensive damage to the cell membranes. Our results revealed the basic properties of three defensins in C. vestalis for the first time, which may pave the way for further study of the functions of defensins in parasitism and innate immunity of C. vestalis.

The rate of wound healing is increased in psoriasis

BACKGROUND

Psoriasis shares many features with wound healing, a process that involves switching keratinocytes from growth to differentiation. Ca2+ is known to regulate this process. The N-methyl-d-aspartate receptor (NMDAR), an ionotropic glutamate receptor found on keratinocytes, is expressed abnormally in psoriasis in vivo.

OBJECTIVES

The goals of this study are to determine whether the rate of healing in the skin of psoriatic individuals differs from that observed in normal skin and whether the keratinocyte hyperproliferation found in psoriasis correlates with expression of specific NMDAR subunits.

METHODS

Three mm punch biopsies were performed on the skin of normal, as well as, involved and uninvolved skin of subjects with psoriasis. On day 0, as well as, on day 6 after the biopsy, photographs were taken and the size of the wounds determined using ImageJ. Using immunohistochemistry, the biopsy material was stained for NMDAR and its subunits.

RESULTS

Involved and uninvolved skin of individuals with psoriasis shows significantly more rapid healing than normal. The NR2C subunit of NMDAR is down-regulated in the basal cell layer of involved and uninvolved epidermis of psoriatic subjects compared to controls. By contrast, cells in the basal cell layer of the uninvolved epidermis showed a significantly greater percent strong staining for NR2D compared to those cells in normal epidermis.

CONCLUSIONS

Wound healing is significantly accelerated in psoriasis compared to normal. Immunohistochemistry showed that the relative intensity of strong immunostaining for subunits of the NMDAR is altered in the basal cell layer in psoriatic skin compared to normal controls. We suggest that these alterations may contribute to the increased rate of wound healing in psoriasis.

Identification of immune response-related genes in the Chinese oak silkworm, Antheraea pernyi by suppression subtractive hybridization

Insects possess an innate immune system that responds to invading microorganisms. In this study, a subtractive cDNA library was constructed to screen for immune response-related genes in the fat bodies of Antheraea pernyi (Lepidoptera: Saturniidae) pupa challenged with Escherichia coli. Four hundred putative EST clones were identified by suppression subtractive hybridization (SSH), including 50 immune response-related genes, three cytoskeleton genes, eight cell cycle and apoptosis genes, five respiration and energy metabolism genes, five transport genes, 40 metabolism genes, ten stress response genes, four transcription and translation regulation genes and 77 unknown genes. To verify the reliability of the SSH data, the transcription of a set of randomly selected immune response-related genes were confirmed by semi-quantitative reverse transcription-PCR (RT-PCR) and real-time quantitative reverse transcription-PCR (qRT-PCR). These identified immune response-related genes provide insight into understanding the innate immunity in A. pernyi.

Dendritic epidermal T cells regulate skin antimicrobial barrier function

The epidermis, the outer layer of the skin, forms a physical and antimicrobial shield to protect the body from environmental threats. Skin injury severely compromises the epidermal barrier and requires immediate repair. Dendritic epidermal T cells (DETC) reside in the murine epidermis where they sense skin injury and serve as regulators and orchestrators of immune responses. Here, we determined that TCR stimulation and skin injury induces IL-17A production by a subset of DETC. This subset of IL-17A-producing DETC was distinct from IFN-γ producers, despite similar surface marker profiles. Functionally, blocking IL-17A or genetic deletion of IL-17A resulted in delayed wound closure in animals. Skin organ cultures from Tcrd-/-, which lack DETC, and Il17a-/- mice both exhibited wound-healing defects. Wound healing was fully restored by the addition of WT DETC, but only partially restored by IL-17A-deficient DETC, demonstrating the importance of IL-17A to wound healing. Following skin injury, DETC-derived IL-17A induced expression of multiple host-defense molecules in epidermal keratinocytes to promote healing. Together, these data provide a mechanistic link between IL-17A production by DETC, host-defense, and wound-healing responses in the skin. These findings establish a critical and unique role of IL-17A-producing DETC in epidermal barrier function and wound healing.

Probiotics in Clostridium difficile infection: reviewing the need for a multistrain probiotic

In the past two years an enormous amount of molecular, genetic, metabolomic and mechanistic data on the host-bacterium interaction, a healthy gut microbiota and a possible role for probiotics in Clostridium difficile infection (CDI) has been accumulated. Also, new hypervirulent strains of C. difficile have emerged. Yet, clinical trials in CDI have been less promising than in antibiotic associated diarrhoea in general, with more meta-analysis than primary papers on CDI-clinical-trials. The fact that C. difficile is a spore former, producing at least three different toxins has not yet been incorporated in the rational design of probiotics for (recurrent) CDI. Here we postulate that the plethora of effects of C. difficile and the vast amount of data on the role of commensal gut residents and probiotics point towards a multistrain mixture of probiotics to reduce CDI, but also to limit (nosocomial) transmission and/or endogenous reinfection. On the basis of a retrospective chart review of a series of ten CDI patients where recurrence was expected, all patients on adjunctive probiotic therapy with multistrain cocktail (Ecologic®AAD/OMNiBiOTiC® 10) showed complete clinical resolution. This result, and recent success in faecal transplants in CDI treatment, are supportive for the rational design of multistrain probiotics for CDI.

Skin microbiota: overview and role in the skin diseases acne vulgaris and rosacea

As the first barrier to environmental exposures, human skin has developed an integrated immune system to protect the inner body from chemical, physical or microbial insults. Microorganisms inhabiting superficial skin layers are known as skin microbiota and include bacteria, viruses, archaea and fungi. The microbiota composition is crucial in the instruction and support of the skin's immune system. Changes in microbiota can be due to individual, environmental or behavioral factors, such as age, climate, hygiene or antibiotic consumption, which can cause dysbiosis. The contribution of skin microbiota to disease development is known in atopic dermatitis, where there is an increase in Staphylococcus aureus. Culture-independent studies have enabled more accurate descriptions of this complex interplay. Microbial imbalance is associated with the development of various diseases. This review focuses on microbial imbalances in acne vulgaris and rosacea.

The cutaneous innate immune response in patients with atopic dermatitis

Orchestrating when and how the cutaneous innate immune system should respond to commensal or pathogenic microbes is a critical function of the epithelium. The cutaneous innate immune system is a key determinant of the physical, chemical, microbial, and immunologic barrier functions of the epidermis. A malfunction in this system can lead to an inadequate host response to a pathogen or a persistent inflammatory state. Atopic dermatitis is the most common inflammatory skin disorder and characterized by abnormalities in both skin barrier structures (stratum corneum and tight junctions), a robust T(H)2 response to environmental antigens, defects in innate immunity, and an altered microbiome. Many of these abnormalities may occur as the consequence of epidermal dysfunction. The epidermis directly interfaces with the environment and, not surprisingly, expresses many pattern recognition receptors that make it a key player in cutaneous innate immune responses to skin infections and injury. This review will discuss the role epidermal innate receptors play in regulation of skin barriers and, where possible, discuss the relevance of these findings for patients with atopic dermatitis.

A common landscape for membrane-active peptides

Three families of membrane-active peptides are commonly found in nature and are classified according to their initial apparent activity. Antimicrobial peptides are ancient components of the innate immune system and typically act by disruption of microbial membranes leading to cell death. Amyloid peptides contribute to the pathology of diverse diseases from Alzheimer's to type II diabetes. Preamyloid states of these peptides can act as toxins by binding to and permeabilizing cellular membranes. Cell-penetrating peptides are natural or engineered short sequences that can spontaneously translocate across a membrane. Despite these differences in classification, many similarities in sequence, structure, and activity suggest that peptides from all three classes act through a small, common set of physical principles. Namely, these peptides alter the Brownian properties of phospholipid bilayers, enhancing the sampling of intrinsic fluctuations that include membrane defects. A complete energy landscape for such systems can be described by the innate membrane properties, differential partition, and the associated kinetics of peptides dividing between surface and defect regions of the bilayer. The goal of this review is to argue that the activities of these membrane-active families of peptides simply represent different facets of what is a shared energy landscape.

Antimicrobial peptides in oyster hemolymph: the bacterial connection

We have explored antimicrobial compounds in oyster hemolymph and purified four active peptides with molecular masses of 4464, 3158, 655 and 636 Da. While no exploitable structural elements were obtained for the former three, a partial amino acid sequence (X-P-P-X-X-I-V) was obtained for the latter, named Cg-636. Due to both its low MM and the presence of exotic amino acid residue (X), we suspected a bacterial origin and tracked cultivable hemolymph-resident bacteria of oyster for their antimicrobial abilities. Supernatants of 224 hemolymph resident bacteria coming from 60 oysters were screened against 10 target bacteria including aquaculture pathogens. Around 2% (5 strains) revealed antimicrobial activities. They belong to Pseudoalteromonas and Vibrio genera. Two closely related strains named hCg-6 and hCg-42 have been shown to produce Bacteriocin-Like Inhibitory Substances (BLIS) even in oyster hemolymph. We report herein first BLIS-producing bacteria isolated from bivalve hemolymph. These results strongly suggest that hemolymph resident bacteria may prevent pathogen establishment and pave the way for considering a role of resident bacteria into bivalve defense.

Human antimicrobial peptide LL-37 modulates proinflammatory responses induced by cytokine milieus and double-stranded RNA in human keratinocytes

Epidermal keratinocytes produce proinflammatory cytokines/chemokines upon stimulation with cytokine milieus and Toll-like receptor ligands, which are considered to reflect epidermal environments in inflamed skin. The human antimicrobial peptide LL-37, besides having microbicidal functions, plays multiple roles as a "host defense peptide" in the immune system. Here, we examined the effect of LL-37 on proinflammatory responses induced by double-stranded RNA (dsRNA) and cytokines in primary human keratinocytes. LL-37 inhibited dsRNA-induced production of thymic stromal lymphopoietin (TSLP), CCL5/RANTES, CXCL10/IP-10, and CXCL8/IL-8, which was attributable to interaction between LL-37 and dsRNA, although LL-37 upregulated CXCL8 expression at an earlier time point (8 h). LL-37 inhibited the increase of CXCL10 and CCL5 induced by TNF-α- and/or IFN-γ but enhanced that of CXCL8. LL-37 and Th17 cytokines (IL-17 and IL-22) synergistically upregulated the expression of CXCL8 and IL-6. LL-37 showed the effects above at a high concentration (25 μg/ml, 5.6 μM). We also examined effects of a peptide with a scrambled LL-37 sequence, which has been frequently used as a negative control, and those of another peptide with the reversed LL-37 sequence, activities of which have not been well investigated. Interestingly, the reversed LL-37 had effects similar to LL-37 but the scrambled LL-37 did not. The modulation by LL-37 of the keratinocyte proinflammatory responses induced by cytokine milieus and dsRNA suggests novel roles for LL-37 in skin inflammation such as the promotion of IL17/IL-22/IL-6-associated psoriasis and suppression of TSLP-associated atopic dermatitis.

Influence of melatonin on the immune system of fish: a review

Endocrine-immune system interactions have been widely demonstrated in mammals, whereas in fish, these relationships remain unclear. Of the organs that constitute the endocrine system, the pineal gland and its secretory product melatonin act in the synchronization of daily and seasonal rhythms in most vertebrates, including fish. Seasonal differences in immunocompetence and disease prevalence have been well documented in humans. Seasonality also strongly influences the life history of fish by controlling the timing of physiological events, such as reproduction, food intake, locomotor activity, and growth performance. Apart from its synchronizing capabilities, the role of melatonin in physiological processes in fish is not thoroughly understood. The purpose of this review is to summarize current studies on the effects of melatonin on the fish immune system. These studies suggest that melatonin represents an important component of fish endocrine-immune system interactions. The elucidation of the defense mechanisms of fish will facilitate the development of health management tools to support the growing finfish aquaculture industry as well as address questions concerning the origins and evolution of the immune system in vertebrates.

Staphylococcus aureus virulence factors in evasion from innate immune defenses in human and animal diseases

In the last decades, Staphylococcus aureus acquired a dramatic relevance in human and veterinary medicine for different reasons, one of them represented by the increasing prevalence of antibiotic resistant strains. However, antibiotic resistance is not the only weapon in the arsenal of S. aureus. Indeed, these bacteria have plenty of virulence factors, including a vast ability to evade host immune defenses. The innate immune system represents the first line of defense against invading pathogens. This system consists of three major effector mechanisms: antimicrobial peptides and enzymes, the complement system and phagocytes. In this review, we focused on S. aureus virulence factors involved in the immune evasion in the first phases of infection: TLR recognition avoidance, adhesins affecting immune response and resistance to host defenses peptides and polypeptides. Studies of innate immune defenses and their role against S. aureus are important in human and veterinary medicine given the problems related to S. aureus antimicrobial resistance. Moreover, due to the pathogen ability to manipulate the immune response, these data are needed to develop efficacious vaccines or molecules against S. aureus.

The Th17 pathway and inflammatory diseases of the intestines, lungs, and skin

The recent discovery of a new CD4+ T cell subset, Th17, has transformed our understanding of the pathogenetic basis of an increasing number of chronic immune-mediated diseases. Particularly in tissues that interface with the microbial environment-such as the intestinal and respiratory tracts and the skin-where most of the Th17 cells in the body reside, dysregulated immunity to self (or the extended self, the diverse microbiota that normally colonize these tissues) can result in chronic inflammatory disease. In this review, we focus on recent advances in the biology of the Th17 pathway and on genome-wide association studies that implicate this immune pathway in human disease involving these tissues.

Structural characterization of de novo designed L5K5W model peptide isomers with potent antimicrobial and varied hemolytic activities

In an effort to develop short antimicrobial peptides with simple amino acid compositions, we generated a series of undecapeptide isomers having the L₅K₅W formula. Amino acid sequences were designed to be perfectly amphipathic when folded into a helical conformation by converging leucines onto one side and lysines onto the other side of the helical axis. The single tryptophans, whose positions were varied in the primary structures, were located commonly at the critical amphipathic interface in the helical wheel projection. Helical conformations and the tryptophanyl environments of the 11 L₅K₅W peptides were confirmed and characterized by circular dichroism, fluorescence and nuclear magnetic resonance spectroscopy. All of the isomers exhibited a potent, broad-spectrum of antibacterial activity with just a slight variance in individual potency, whereas their hemolytic activities against human erythrocytes were significantly diversified. Interestingly, helical dispositions and fluorescence blue shifts of the peptides in aqueous trifluoroethanol solutions, rather than in detergent micelles, showed a marked linear correlation with their hemolytic potency. These results demonstrate that our de novo design strategy for amphipathic helical model peptides is effective for developing novel antimicrobial peptides and their hemolytic activities can be estimated in correlation with structural parameters.

Molecular dermatology comes of age

Groundbreaking advances on the molecular and cellular physiological and physiopathological skin processes, including the complete sequencing of the genome of several species and the increased availability of gene-modified organisms, paved the way to firmly establishing molecular approaches and methods in experimental, translational, and clinical dermatology. As a result, newly developed experimental ex vivo assays and animal models prove exquisite tools for addressing fundamental physiological cutaneous processes and pathogenic mechanisms of skin diseases. A plethora of new findings that were generated using these experimental tools serve as a strong basis for intense translational research efforts aiming at developing new, specific, and sensitive diagnostic tests and efficient "personalized" therapies with less side-effects. Consequently, a broad array of molecular diagnostic tests and therapies for a wide spectrum of skin diseases ranging from genodermatoses through skin neoplasms, allergy, inflammatory and autoimmune diseases, are already routinely used in the clinical dermatology practice. This article highlights several major developments in molecular experimental and clinical dermatology.

Interaction of antimicrobial peptide magainin 2 with gangliosides as a target for human cell binding

Understanding how antimicrobial peptides (AMPs) interact with human cells is important to the development of antimicrobial agents as well as anticancer drugs. However, little is known about the mechanisms by which AMPs bind to cells and exert cytotoxicity. Negatively charged gangliosides on the cell surface are a potential target for cell binding. In this study, we investigated the interaction of F5W-magainin 2 (MG) with gangliosides in detail. MG was colocalized with gangliosides on HeLa cells, indicating that gangliosides act as a receptor for MG. MG also bound to gangliosides in model membranes. The affinity increased with the number of negatively charged sialic acid residues. Physicochemical studies revealed that MG interacts with the monosialoganglioside GM1 differently from the typical bacterial anionic phospholipid phosphatidylglycerol. MG bound to GM1 more strongly than to phosphatidylglycerol, and the binding isotherm for GM1 could be analyzed by the Langmuir equation assuming charge neutralization. This is in contrast to the binding of AMPs to phosphatidylglycerol-containing bilayers, which has been described by the electrostatic attraction-surface partitioning model. Fluorescence resonance energy transfer experiments supported the clustering of GM1, but not phosphatidylglycerol, by MG. Quenching data suggested that MG is bound to the sugar region of GM1. The bound peptide assumed a helical structure and induced the leakage of calcein and the coupled flip-flop of lipids, indicating the peptide also forms a toroidal pore in GM1-containing vesicles. However, the membrane permeabilizing activity was weaker against GM1-containing membranes than phosphatidylglycerol-doped liposomes in accordance with the trapping of the peptide in the sugar region. These results shed light on AMP-human cell interaction.

Identification of 15 new psoriasis susceptibility loci highlights the role of innate immunity

To gain further insight into the genetic architecture of psoriasis, we conducted a meta-analysis of 3 genome-wide association studies (GWAS) and 2 independent data sets genotyped on the Immunochip, including 10,588 cases and 22,806 controls. We identified 15 new susceptibility loci, increasing to 36 the number associated with psoriasis in European individuals. We also identified, using conditional analyses, five independent signals within previously known loci. The newly identified loci shared with other autoimmune diseases include candidate genes with roles in regulating T-cell function (such as RUNX3, TAGAP and STAT3). Notably, they included candidate genes whose products are involved in innate host defense, including interferon-mediated antiviral responses (DDX58), macrophage activation (ZC3H12C) and nuclear factor (NF)-κB signaling (CARD14 and CARM1). These results portend a better understanding of shared and distinctive genetic determinants of immune-mediated inflammatory disorders and emphasize the importance of the skin in innate and acquired host defense.

Insight into newly discovered innate immune modulation in atopic dermatitis

Atopic dermatitis (AD) is a highly pruritic, chronic relapsing inflammatory skin disease characterized by innate and adaptive immune reactions. In AD, innate immune mechanisms such as pattern recognition receptors and antimicrobial peptides have been investigated in detail, but recently, epidermis-derived cytokines, namely thymic stromal lymphopoietin (TSLP), IL-25 and IL-33, were shown to participate in innate immune reactions independently of adaptive immunity. In addition to conventional innate cells, such as mast cells, basophils and eosinophils, Th2 cytokine-producing invariant natural killer T (iNKT) cells, innate lymphoid cells (ILCs) and Th17/Th22 cytokine-producing innate cells - iNKT cells and natural killer (NK)-like cells - can participate in innate immune modulation in AD. Accordingly, early control of innate immune responses in AD before activation of adaptive immune responses by conventional T and B cells that perpetuate chronic skin inflammation may adequately alleviate acute exacerbations of AD. Therefore, we hypothesized that select immune modulators targeting the innate immune response could potentially be used for individualized treatment of AD.

Genomic expression analyses reveal lysosomal, innate immunity proteins, as disease correlates in murine models of a lysosomal storage disorder

Niemann-Pick Type C (NPC) disease is a rare, genetic, lysosomal disorder with progressive neurodegeneration. Poor understanding of the pathophysiology and a lack of blood-based diagnostic markers are major hurdles in the treatment and management of NPC and several additional, neurological lysosomal disorders. To identify disease severity correlates, we undertook whole genome expression profiling of sentinel organs, brain, liver, and spleen of Balb/c Npc1^−/− mice relative to Npc1^+/− at an asymptomatic stage, as well as early- and late-symptomatic stages. Unexpectedly, we found prominent up regulation of innate immunity genes with age-dependent change in their expression, in all three organs. We shortlisted a set of 12 secretory genes whose expression steadily increased with age in both brain and liver, as potential plasma correlates of neurological and/or liver disease. Ten were innate immune genes with eight ascribed to lysosomes. Several are known to be elevated in diseased organs of murine models of other lysosomal diseases including Gaucher’s disease, Sandhoff disease and MPSIIIB. We validated the top candidate lysozyme, in the plasma of Npc1^−/− as well as Balb/c Npc1^nmf164 mice (bearing a point mutation closer to human disease mutants) and show its reduction in response to an emerging therapeutic. We further established elevation of innate immunity in Npc1^−/− mice through multiple functional assays including inhibition of bacterial infection as well as cellular analysis and immunohistochemistry. These data revealed neutrophil elevation in the Npc1^−/− spleen and liver (where large foci were detected proximal to damaged tissue). Together our results yield a set of lysosomal, secretory innate immunity genes that have potential to be developed as pan or specific plasma markers for neurological diseases associated with lysosomal storage and where diagnosis is a major problem. Further, the accumulation of neutrophils in diseased organs (hitherto not associated with NPC) suggests their role in pathophysiology and disease exacerbation.

Comparative genomics analysis of five families of antimicrobial peptide-like genes in seven ant species

Ants, as eusocial insects, live in dense groups with high connectivity, increasing the risk of pathogen spread and possibly driving the evolution of their antimicrobial immune system. Draft genomes of seven ant species provide a new source to undertake comparative study of their antimicrobial peptides (AMPs), key components of insect innate immunity. By using computational approaches, we analyzed five AMP families that include abaecins, hymenoptaecins, insect defensins, tachystatins, and crustins in ants, which comprise 69 new members. Among them, a new type of proline-rich abaecins was recognized and they are exclusively present in ants. Hymenoptaecins, a family of glycine-rich AMPs from Hymenoptera and Diptera, exhibit variable numbers of intragenic tandem repeats in a lineage-specific manner and all hymenoptaecins in ants have evolved an acidic C-terminal propeptide. In some ant species, insect defensins with the cysteine-stabilized α-helical and β-sheet (CSαβ) fold and tachystatin-like AMPs with the inhibitor cysteine knot (ICK) fold have undergone gene expansion and differential gene loss. Moreover, extensive sequence diversity exists in the C-termini of the defensins and the ICK-type peptides and the n-loop of the defensins. Also, we identified for the first time a crustin-type AMP in ants, which are only known in crustaceans previously. These ant crustins evolutionarily gain an aromatic amino acid-rich insertion when compared with those of crustaceans. Our work not only enlarges the insect AMP resource, but also sheds light on the complexity and dynamic evolution of AMPs in ants.

Antimicrobial peptide control of pathogenic microorganisms of the oral cavity: a review of the literature

Antimicrobial peptides, molecules produced in many different organisms, have high biocidal activity against several microorganisms. However, several questions about these molecules remain unclear. Therefore, this report details a systematic survey of the literature on the use of antimicrobial peptides against oral pathogens and indicates which peptides and microorganisms are most extensively studied. Articles were located using the PubMed and Science Direct databases with the following inclusion criteria: publication date between 2002 and 2011; keywords "biofilm OR biological film OR biological layer OR bacterial growth" AND "peptide" AND "oral cavity OR mouth OR buccal mucosa OR oral mucosa OR mouth mucosa"; and abstract in English. A total of 73 articles were selected after refinement of the data. An increase in publications focusing on the use of antimicrobial peptides against oral microorganisms was observed. In addition, the peptides produced by cells of the oral mucosa (defensins, LL-37 and histatins) as well as Streptococcus mutans (among cariogenic bacteria) and Porphyromonas gingivalis (among periodontal bacteria) were the most studied subjects. It was concluded that the use of antimicrobial peptides as a tool for microbial control is of increasing importance, likely due to its widespread use, mechanism of action, and low rates of bacterial resistance.

Skin micro-organs from several frog species secrete a repertoire of powerful antimicrobials in culture

This work is an attempt to take advantage of the rich biodiversity that exists in Colombia in order to start a systematic analysis of antimicrobial substances that have emerged through amphibian evolution. For this purpose we have developed a technique to grow intact frog skin derived micro-organs (SMOs) in vitro in the absence of serum. We show that in SMOs, the skin glands remain intact and continue to secrete into the medium substances with potent antibacterial activity, for several days in culture. Our strategy has been to create a bank of substances secreted by amphibian skin from different species. This bank contains at present around 50 species and is of particular importance as some of the species are in danger of disappearing. We show that some of the species tested displayed very strong antibacterial activity without being toxic to somatic cell lines, even at 10-fold higher concentration.