Defensins and acne

Calprotectin may be positively associated with the severity of acne vulgaris

Background and objective: Acne vulgaris (AV) is a common skin disease of sebaceous hair follicles. Many factors are associated with the occurrence and severity of acne, while the exact etiology remains incompletely understood. The current study was aimed to investigate the association between the severity of acne and serum zinc, copper, and calprotectin. Methods: Fifty patients with AV were recruited in the study as well as 25 healthy age and sex-matched individuals as controls. The acne severity was classified into mild (n=21), moderate (n=16), and severe acne (n=14) according to the global acne grading system (GAGS). Serum levels of zinc, acne and calprotectin were evaluated by enzyme-linked immunosorbent assay (ELISA). The gained data were analyzed using GraphPad Prism software. Results: Insignificant difference was found in zinc and copper levels between controls and AV patients, except in severe AV, where the patients displayed significant elevation in serum copper level (p<0.05) as compared to that of mild AV. The calprotectin concentration was significantly higher (p<0.001) in all AV patients, when compared with healthy subjects, which was positively correlated with the disease severity. No gender difference was noted for all measured biomarkers. Conclusions: Our study suggests a possible association between calprotectin and acne inflammation, which requires validation in large-scale studies.

Acne Vulgaris is Associated with the Human β-Defensin 1-Gene Polymorphisms in Han Chinese Ethnic Group Patients

Objective

To study the relationship between the single nucleotide polymorphisms (SNPs) of the human β-defensin 1-gene (DEFB1) and the genetic susceptibility of acne vulgaris in the Han Chinese ethnic group.

Methods

A total of 104 patients with acne vulgaris and 126 healthy participants were included in our study. We analyzed the association between acne vulgaris and the polymorphisms in the DEFB1 G-52A, C-44G, and G-20A gene. We then analyzed the relationship between the different genotypes and the susceptibility to acne vulgaris.

Results

The frequency of DEFB1 C-44G genetic polymorphisms between the acne vulgaris group and the control group was significantly different (P < 0.05). The frequency of DEFB1 G-20A genetic polymorphisms between the acne vulgaris group and the control group was also significantly different (P < 0.05).

Conclusion

The −44G or −20A allele showed a low expression in acne vulgaris, which has already been shown to correlate with the low risk of acne vulgaris among Chinese Han patients. This further supports the contribution of the DEFB1 gene to the pathogenesis of acne.

In Vitro and Randomized, Double-Blind, Placebo-Controlled Trial to Determine the Efficacy and Safety of Nine Antiacne Medicinal Plants

The present in vitro and randomized, double‐blind, placebo‐controlled trial aims to determine the efficacy and safety of nine Mediterranean antiacne medicinal plants. The antimicrobial, antisebum, and anti-inflammatory activities of the plant extracts were evaluated in cells from the immortalized human keratinocytes (HaCaT) and human monocytic cell line (THP-1) as well as in a double-blind, randomized, and placebo‐controlled trial. Most of the extracts showed no significant cytotoxic effects on HaCaT cells up to 250 μg/ml. Inula helenium (IH) and Saponaria officinalis (SO) inhibited sebum production at 90 μg/ml and 30 μg/ml, respectively. The inhibition effect of SO on the growth of Cutibacterium acnes was 1.2 times higher than that of chloramphenicol. IH and SO extracts significantly inhibited the lipopolysaccharide- (LPS-) induced IL-6 and TNF-α production in THP-1 cells reaching the control levels of untreated cells at a concentration of 250 μg/ml. SO, IH, and Solanum nigrum (SN) extracts inhibited the nitric oxide (NO) production in a dose-dependent manner. Based on these results, an antiacne herbal cream (AHC) was prepared from different portions of extracts from SO, IH, and SN, and its efficacy was evaluated in a double-blind, randomized, and controlled efficacy study with 41 acne patients, ages 18–24, who were asked to apply AHC (n = 27) or a placebo (n = 14) two to three times daily for six weeks. Results obtained indicate that the AHC has unique synergistic effects that halt sebum production, combined with highly antiseptic and anti-inflammatory activity, in which 54.95% (t = 19.37 P < 0.001) of acne inflammatory and noninflammatory lesions disappeared after two weeks, 85.3%, after five weeks (t = 14.19 P < 0.001), and 91.4%, at the end of the sixth week of application (t = 5.7 P < 0.001). In conclusion, SO, IH, and SN as single extracts and in combination as AHC showed significant antimicrobial, antisebum, and anti-inflammatory activities in vitro and in a double-blind, randomized, and controlled antiacne efficacy. Therefore, AHC represents an interesting alternative treatment for acne.

Genome-wide meta-analysis implicates mediators of hair follicle development and morphogenesis in risk for severe acne

Acne vulgaris is a highly heritable common, chronic inflammatory disease of the skin for which five genetic risk loci have so far been identified. Here, we perform a genome-wide association study of 3823 cases and 16,144 controls followed by meta-analysis with summary statistics from a previous study, with a total sample size of 26,722. We identify 20 independent association signals at 15 risk loci, 12 of which have not been previously implicated in the disease. Likely causal variants disrupt the coding region of WNT10A and a P63 transcription factor binding site in SEMA4B. Risk alleles at the 1q25 locus are associated with increased expression of LAMC2, in which biallelic loss-of-function mutations cause the blistering skin disease epidermolysis bullosa. These findings indicate that variation affecting the structure and maintenance of the skin, in particular the pilosebaceous unit, is a critical aspect of the genetic predisposition to severe acne.

Acne vulgaris is a chronic inflammation of the skin, the genetic basis of which is incompletely understood. Here, Petridis et al. perform GWAS and meta-analysis for acne in 26,722 individuals and identify 12 novel risk loci that implicate structure and maintenance of the skin in severe acne risk.

Bio-based topical system for enhanced salicylic acid delivery: preparation and performance of gels

Objectives

New salicylic acid (SA)-loaded gels were developed using excipients made from renewable materials, and our goal was to improve drug permeation in the topical treatment of acne vulgaris.

Methods

We studied the preparation parameters to obtain suitable gel formulations. Only naturally occurring polymers were used as gelling agents. Two hydrogels and three lipogels were selected and characterized in terms of drug loading, pH, viability cells, rheology, mechanical properties and in vitro permeation; these hydrogels and lipogels were compared with the traditional ointment. We also evaluated skin parameters before and after gel application.

Key findings

The formulations that we studied are non-Newtonian fluids; they have high drug loading and suitable mechanical properties. Lipogels exhibit a slower and more linear in vitro permeation profile compared with hydrogels. The different vehicles that we used affected drug permeation and improve patient compliance. Cytotoxicity studies suggest that all of the formulations are non-toxic.

Conclusions

Lipogels demonstrate appropriate technological features and improved performance compared with the traditional ointment with regard to their composition. Lipogels may represent a new bio-based topical system for SA delivery. The use of ‘green’ excipients leads to ‘skin-friendly’ formulations that are able to satisfy environmental safety.

The Microbiota of the Human Skin

The aim of this chapter is to sum up important progress in the field of human skin microbiota research that was achieved over the last years.The human skin is one of the largest and most versatile organs of the human body. Owing to its function as a protective interface between the largely sterile interior of the human body and the highly microbially contaminated outer environment, it is densely colonized with a diverse and active microbiota. This skin microbiota is of high importance for human health and well-being. It is implicated in several severe skin diseases and plays a major role in wound infections. Many less severe, but negatively perceived cosmetic skin phenomena are linked with skin microbes, too. In addition, skin microorganisms, in particular on the human hands, are crucial for the field of hygiene research. Notably, apart from being only a potential source of disease and contamination, the skin microbiota also contributes to the protective functions of the human skin in many ways. Finally, the analysis of structure and function of the human skin microbiota is interesting from a basic, evolutionary perspective on human microbe interactions.Key questions in the field of skin microbiota research deal with (a) a deeper understanding of the structure (species inventory) and function (physiology) of the healthy human skin microbiota in space and time, (b) the distinction of resident and transient skin microbiota members,

Molecular cartography of the human skin surface in 3D

The human skin is an organ with a surface area of 1.5-2 m(2) that provides our interface with the environment. The molecular composition of this organ is derived from host cells, microbiota, and external molecules. The chemical makeup of the skin surface is largely undefined. Here we advance the technologies needed to explore the topographical distribution of skin molecules, using 3D mapping of mass spectrometry data and microbial 16S rRNA amplicon sequences. Our 3D maps reveal that the molecular composition of skin has diverse distributions and that the composition is defined not only by skin cells and microbes but also by our daily routines, including the application of hygiene products. The technological development of these maps lays a foundation for studying the spatial relationships of human skin with hygiene, the microbiota, and environment, with potential for developing predictive models of skin phenotypes tailored to individual health.

What is the role of antimicrobial peptides (AMP) in acne vulgaris?

Acne vulgaris is the most common disorder of the pilosebaceous unit leading to inflamed skin characterized by the formation of comedones, papules, pustules and scarring. There is increasing evidence that the abundance of Propionibacterium acnes (P. acnes) in the inflamed acne lesions triggers inflammation. Therefore, in addition to treatment with retinoids, the use of antimicrobial agents has been established as a treatment option for acne. This indicates that antimicrobial mechanisms to control the growth of P. acnes may have an important influence on the severity of inflammatory acne. One import antimicrobial innate defense system comprises the production of antimicrobial peptides (AMP), small molecules with a broad spectrum of antimicrobial activity as well as immunomodulatory properties. Although the role of AMP in acne is still emerging, there is increasing evidence that AMP may be of importance in acne. The aim of this viewpoint is to provide some hypotheses about the potential function of AMP in the pathogenesis of acne and to discuss potential AMP-based therapies for the treatment of acne.

Staphylococcus colonization of the skin and antimicrobial peptides

Staphylococci are the most abundant skin-colonizing bacteria and the most important causes of nosocomial infections and community-associated skin infections. Molecular determinants of staphylococcal skin colonization include surface polymers and proteins that promote adhesion and aggregation, and a wide variety of mechanisms to evade acquired and innate host defenses. Antimicrobial peptides (AMPs) likely play a central role in providing immunity to bacterial colonization on human epithelia. Recent research has shown that staphylococci have a broad arsenal to combat AMP activity, and can regulate expression of AMP-resistance mechanisms depending on the presence of AMPs. While direct in vivo evidence is still lacking, this suggests that the interplay between AMPs and AMP resistance mechanisms during evolution had a crucial role in rendering staphylococci efficient colonizers of human skin.

Protecting the boundary: the sentinel role of host defense peptides in the skin

The skin is our primary shield against microbial pathogens and has evolved innate and adaptive strategies to enhance immunity in response to injury or microbial insult. The study of antimicrobial peptide (AMP) production in mammalian skin has revealed several of the elegant strategies that AMPs use to prevent infection. AMPs are inducible by both infection and injury and protect the host by directly killing pathogens and/or acting as multifunctional effector molecules that trigger cellular responses to aid in the anti-infective and repair response. Depending on the specific AMP, these molecules can influence cytokine production, cell migration, cell proliferation, differentiation, angiogenesis and wound healing. Abnormal production of AMPs has been associated with the pathogenesis of several cutaneous diseases and plays a role in determining a patient's susceptibility to pathogens. This review will discuss current research on the regulation and function of AMPs in the skin and in skin disorders.

Protease-activated receptor-2 mediates the expression of inflammatory cytokines, antimicrobial peptides, and matrix metalloproteinases in keratinocytes in response to Propionibacterium acnes

Propionibacterium acnes (P. acnes) has been known to produce various exogenous proteases, however, their role in acne pathogenesis remains largely unknown. Proteases elicit cellular responses, at least in part, via proteinase-activated receptor-2 (PAR-2), which is known to mediate inflammation and immune response. In this study, we investigated whether proteases from P. acnes could activate PAR-2 on keratinocytes and induce pro-inflammatory cytokines, antimicrobial peptides (AMPs), and matrix metalloproteinases (MMPs) via PAR-2 signaling. We examined PAR-2 expression and protease activity in acne lesions using immunofluorescence staining and in situ zymography. The effect of the culture supernatant of P. acnes on Ca(2+) signaling in immortalized keratinocytes (HaCaT) was measured using a fluorescence method. HaCaT cells were treated with P. acnes strain ATCC 6919 culture supernatant, with or without pretreatment with serine protease inhibitor or selective PAR-2 antagonist and the gene expression of pro-inflammatory cytokines, AMPs, and MMPs was detected using real-time reverse transcription-polymerase chain reaction. We found that the protease activity and PAR-2 expression were increased in acne lesions. The P. acnes culture supernatant induced calcium signaling in keratinocytes via PAR-2 and stimulated the mRNA expression of interleukin (IL)-1α, -8, tumor necrosis factor (TNF)-α, human beta defensin (hBD)-2, LL-37, MMP-1, -2, -3, -9, and -13 in keratinocytes, which was significantly inhibited by serine protease inhibitor as well as selective PAR-2 specific antagonist. These results indicate that PAR-2 plays an important role in the pathogenesis of acne by inducing inflammatory mediators in response to proteases secreted from P. acnes.

Interaction of human β-defensin 2 (HBD2) with glycosaminoglycans

Human β-defensin 2 (HBD2) is a member of the defensin family of antimicrobial peptides that plays important roles in the innate and adaptive immune system of both vertebrates and invertebrates. In addition to their direct bactericidal action, defensins are also involved in chemotaxis and Toll-like receptor activation. In analogy to chemokine/glycosaminoglycan (GAG) interactions, GAG-defensin complexes are likely to play an important role in chemotaxis and in presenting defensins to their receptors. Using a gel mobility shift assay, we found that HBD2 bound to a range of GAGs including heparin/heparan sulfate (HS), dermatan sulfate (DS), and chondroitin sulfate. We used NMR spectroscopy of (15)N-labeled HBD2 to map the binding sites for two GAG model compounds, a heparin/HS pentasaccharide (fondaparinux sodium; FX) and enzymatically prepared DS hexasaccharide (DSdp6). We identified a number of basic amino acids that form a common ligand binding site, which indicated that these interactions are predominantly electrostatic. The dissociation constant of the [DSdp6-HBD2] complex was determined by NMR spectroscopy to be 5 ± 5 μM. Binding of FX could not be quantified because of slow exchange on the NMR chemical shift time scale. FX was found to induce HBD2 dimerization as evidenced by the analysis of diffusion coefficients, (15)N relaxation, and nESI-MS measurements. The formation of FX-bridged HBD2 dimers exhibited features of a cooperative binding mechanism. In contrast, the complex with DSdp6 was found to be mostly monomeric.

[Pre- and probiotic cosmetics]

The human skin provides a habitat for a variety of microorganisms, the skin microflora. There is a complex network of interactions between the microbes and cells of the epidermis. Modern analytical methods in molecular biology have revealed new insights into this complex diversity of partially unculturable microbial organisms. Most of the resident microbes on healthy skin can be regarded as being harmless or even beneficial to skin. In the case of diseases with some imbalance in microorganisms, such as impure skin/mild acne or dry skin/mild atopic dermatitis, pre- and probiotic concepts represent an effective alternative to strictly antibacterial products. Prebiotic actives rebalance the skin microflora while probiotic approaches predominantly consist of applying an inactivated microbial biomass of beneficial bacteria. Several examples of successful in vivo studies illustrate this new principle for gentle cosmetics derived from the food sector.

Significant upregulation of antimicrobial peptides and proteins in lichen sclerosus

BACKGROUND

Lichen sclerosus (LS) is a chronic inflammatory T cell-driven sclerotic skin condition in which skin barrier disruption frequently occurs. Inflamed and injured epithelia are a particularly rich source of antimicrobial peptides and proteins (AMPs).

OBJECTIVES

We aimed to investigate for the first time the expression pattern of AMPs in lesions of LS as compared with healthy skin.

METHODS

Twenty-four women with LS as well as 10 healthy women were included in the study. In order to assess the expression of human beta-defensin (hBD)-1, hBD-2, hBD-3, psoriasin (S100A7), the cathelicidin LL-37 and RNase 7, real-time reverse transcriptase-polymerase chain reaction and immunohistochemistry were performed on skin specimens obtained from lesional and healthy skin of the genital region, respectively.

RESULTS

Median hBD-2 mRNA levels observed in LS were significantly higher than in controls (0.15 vs. 0.008; P = 0.0037). Moreover, psoriasin (98.2 vs. 28.1; P = 0.0052) mRNA expression was significantly higher in LS lesions as compared with controls. Significant differences in mRNA expression of hBD-2 and psoriasin were also confirmed by immunohistochemistry. For hBD-1, hBD-3, LL-37 and RNase 7, levels did not differ significantly or were significant only at the gene level but not protein level.

CONCLUSIONS

We have demonstrated that hBD-2 and psoriasin expression levels in lesional skin of patients with LS are significantly increased when compared with healthy controls. Whether this observation simply reflects an innate defence response caused by an increased risk of local infection, or whether our data indicate a pathogenetic role of AMPs in LS, will be addressed in future studies.

Toll-like receptor agonists regulate β-defensin 2 release in hair follicle

BACKGROUND

Skin is constantly in contact with different pathogens, which are present in the environment. The hair follicle is particularly susceptible to this microbial invasion as it offers an easy way of access for microorganisms; for this reason it is equipped with defence mechanisms to avoid frequent infections.

OBJECTIVES

To analyse the expression pattern of four different members of the toll-like receptor (TLR) family in murine hair follicles and to evaluate the effects of their activation by their specific microbiota-derived agonists, in terms of production of the antimicrobial peptide beta-defensin 2 (DEFB2).

METHODS

TLR and DEFB2 protein expression was investigated by immunohistochemistry on murine skin samples.

RESULTS

Murine hair follicle expresses TLR2, TLR4 and TLR5; agonists of TLR2, TLR4 and TLR5 but not of TLR9 induced DEFB2 production in this compartment. The strongest DEFB2 expression was observed following TLR4 activation by lipopolysaccharide.

CONCLUSIONS

Our data show that the hair follicle is equipped with TLR2, TLR4 and TLR5, and that these receptors are able to respond to microbial stimuli inducing the production of DEFB2 by epithelial cells. This immune response might be important in preserving the skin from microorganism infections.

Antimicrobial peptides: an essential component of the skin defensive barrier

The skin is positioned at the interface between an organism's internal milieu and an external environment characterized by constant assault with potential microbial pathogens. While the skin was formerly considered an inactive physical protective barrier that participates in host immune defense merely by blocking entry of microbial pathogens, it is now apparent that a major role of the skin is to defend the body by rapidly mounting an innate immune response to injury and microbial insult. In the skin, both resident and infiltrating cells synthesize and secrete small peptides that demonstrate broad-spectrum antimicrobial activity against bacteria, fungi, and enveloped viruses. Antimicrobial peptides also act as multifunctional immune effectors by stimulating cytokine and chemokine production, angiogenesis, and wound healing. Cathelicidins and defensins comprise two major families of skin-derived antimicrobial peptides, although numerous others have been described. Many such immune defense molecules are currently being developed therapeutically in an attempt to combat growing bacterial resistance to conventional antibiotics.

Propionibacterium acnes and lipopolysaccharide induce the expression of antimicrobial peptides and proinflammatory cytokines/chemokines in human sebocytes

Acne is a common skin disorder of the pilosebaceous unit. In addition to genetic, hormonal and environmental factors, abnormal colonization by Propionibacterium acnes has been implicated in the occurrence of acne via the induction of inflammatory mediators. To gain more insight into the role that sebocytes play in the innate immune response of the skin, particularly in acne, we compared the antimicrobial peptide and proinflammatory cytokine/chemokine expression at mRNA and protein levels, as well as the viability and differentiation of SZ95 sebocytes in response to co-culture with representative isolates of P. acnes type IA and type IB as well as Escherichia coli-derived lipopolysaccharide (LPS). We found that, in vitro, P. acnes type IA and IB isolates and LPS induced human beta-defensin-2 and proinflammatory cytokine/chemokine expression, and influenced sebocyte viability and differentiation. Our results provide evidence that sebocytes are capable of producing proinflammatory cytokines/chemokines and antimicrobial peptides, which may have a role in acne pathogenesis. Furthermore, since P. acnes types IA and IB differentially affect both the differentiation and viability of sebocytes, our data demonstrate that different strains of P. acnes vary in their capacity to stimulate an inflammatory response within the pilosebaceous follicle.

Antimicrobial peptides: effectors of innate immunity in the skin

The ability of the cutaneous barrier to help defend the body against pathogens relies on both acquired and innate immune responses. Recently, a large body of research has suggested that a critical component of the innate immune response in the skin is 3 antimicrobial peptides: the cathelicidins, defensins, and dermcidins. These 3 classes of peptides have been shown to act as antimicrobials by directly inhibiting pathogen growth as well as potentiating other branches of the innate, humoral, and cell-mediated immune system. Here, we review the antimicrobial peptides with an emphasis on their role in the cutaneous immune response. We present an overview of defensin, cathelicidin, and dermcidin physiology, elucidating their various functions. In addition, we delve into the role of these peptides in specific dermatologic conditions including wound healing, atopy, and microbial infection. Finally, we discuss the future of antimicrobial peptide research including therapeutic options.

Antimikrobielle Peptide

Human antimicrobial peptides play a substantial role in the immune response to various dermatological diseases, such as acne, atopic dermatitis and psoriasis vulgaris, and even mucosal HIV-protection is mediated inter alia by antimicrobial peptides. In wound healing, the antimicrobial and immune-modulating properties of, in particular, human defensins and cathelicidins can affect important controlling factors. For example, the interaction between different antimicrobial peptides and growth factors supports neoangiogenesis. Although further clinical investigations are necessary to identify the exact effects of antimicrobial peptides in chronic wounds, such peptides could be a promising therapeutic option in the near future for the treatment of patients with chronic wounds by promoting endogen expression or exogenous supplementation.

Cutaneous Defense Mechanisms by Antimicrobial Peptides

The skin actively contributes to host defense by mounting an innate immune response that includes the production of antimicrobial peptides. These peptides, which include but are not limited to the cathelicidin and defensin gene families, provide rapid, broad-spectrum defense against infection by acting as natural antibiotics and by participating in host cell processes involved in immune defense. This review discusses the biology and clinical relevance of antimicrobial peptides expressed in the skin. The importance of the epithelial contribution to host immunity is evident, as alterations in antimicrobial peptide expression have been associated with various pathologic processes.

The Role of Toll-Like Receptors in the Pathophysiology of Acne

Acne vulgaris is a common cutaneous disorder of the pilosebaceous follicle, affecting more than 45 million people in the United States alone. The pathogenesis of acne is multifactorial, involving abnormal hyperkeratinization, increased sebum production, hormones, cutaneous microbes, and immunological mechanisms. Many of the immunological processes that contribute to the formation of acne lesions take place at the very site of disease, the skin. Skin is an important component of the innate immune system, providing both physical barriers and rapid cellular responses by keratinocytes, Langerhans cells, and other infiltrating inflammatory cells. In this review, we discuss the ability of the innate immune system to use Toll-like receptors (TLRs) to recognize microbial patterns and initiate immune responses in cutaneous disorders. Because TLRs are vital players in infectious and inflammatory diseases, they are potential therapeutic targets. Indeed, the ability of TLRs to combat disease already has been harnessed through the development of drugs that act as TLR agonists. A better understanding of TLRs will allow for the development of new therapeutic options for cutaneous inflammatory diseases such as acne.

Acne update: 2004

PURPOSE OF REVIEW

Acne vulgaris is a common skin disorder among children and young adults that carries enormous financial and psychosocial impact. Contemporary therapies attempt to address factors underlying acne as a disorder of the pilosebaceous unit. These longstanding paradigms regarding pathogenesis and treatment continue to evolve in light of recent work on this ubiquitous disease.

RECENT FINDINGS

This review focuses on new literature that has emerged regarding the biology of the folliculosebaceous unit, the identification of particular mediators responsible for inflammatory acne, the use of topical and systemic retinoids in acne therapy, and approaches to address the emergence of antibiotic-resistant Propionibacterium acnes strains. In addition, the use of several novel therapeutic avenues is discussed, including combination therapies, lipoxygenase inhibitors, and lasers.

SUMMARY

As the understanding of the factors that initiate and exacerbate acne vulgaris continues to increase, so does the diversity of therapeutic options. Rational use of available treatment options based on the type and severity of acne lesions is a key component of successful acne therapy and allows the physician who treats adolescents with acne to provide optimum care.