Effects of staphylococci on cytokine production from human keratinocytes

Non-invasive evaluation of cytokine expression using the cerumen of dogs with otitis externa

The development of a non-invasive method to analyze cytokine expression in the skin will provide further understanding of inflammatory skin disorders. This study aimed to evaluate cytokine expression in the skin through cerumen swabbing in dogs with otitis externa (OE) and to investigate whether increased cytokine expression in infected OE reflects the inflammatory status of the ear canal. Three groups consisting of control dogs (n = 24), dogs with ceruminous Malassezia OE (n = 25), and dogs with suppurative bacterial OE (n = 15) were included in the study. The concentrations of keratinocyte-derived cytokines including Interleukin (IL)-8/chemokine ligand (CXCL)8, IL-10, IL-6, Tumor necrosis factor (TNF)-α, and IL-1ß in the cerumen of the ear canal of the included patients were analyzed using commercial ELISA kits. Additionally, correlations between cytokine levels and cytology scores (of Malassezia yeasts, cocci/rod-shaped bacteria, and inflammatory cells) were assessed. IL-8/CXCL8 concentrations were significantly higher in dogs with ceruminous Malassezia OE and dogs with suppurative bacterial OE than in control dogs. Furthermore, IL-8/CXCL8 concentrations positively correlated with Malassezia scores in dogs with ceruminous OE (r = 0.630) and with bacterial scores in dogs with suppurative OE (r = 0.601). In addition, increased expression of IL-6 and IL-1ß were detected in dogs with suppurative bacterial OE compared to those with Malassezia OE and control dogs, and showed positive correlation with inflammatory cell scores IL-6 r = 0.520, IL-1ß; r = 0.680). Therefore, keratinocyte-derived cytokines could be evaluated using non-invasive methods such as cerumen swabbing in dogs with OE.

Inflammatory Response Against Staphylococcus aureus via Intracellular Sensing of Nucleic Acids in Keratinocytes

Staphylococcus aureus is one of the clinically most relevant pathogens causing infections. Humans are often exposed to S. aureus. In approximately one-third of the healthy population it can be found on the skin either for long or short periods as colonizing "commensals", without inducing infections or an inflammatory immune response. While tolerating S. aureus seems to be limited to certain individuals and time periods in most cases, Staphylococcus epidermidis is tolerated permanently on the skin of almost all individuals without activating overwhelming skin inflammation. To investigate this, we co-cultured a keratinocyte cell line (HaCaT) with viable S. aureus or S. epidermidis to study the differences in the immune activation. S. aureus activated keratinocytes depicted by a profound IL-6 and IL-8 response, whereas S. epidermidis did not. Our data indicate that internalization of S. aureus and the subsequent intracellular sensing of bacterial nucleic acid may be essential for initiating inflammatory response in keratinocytes. Internalized dsRNA activates IL-6 and IL-8 release, but not TNF-α or IFNs by human keratinocytes. This is a non-specific effect of dsRNA, which can be induced using Poly(I:C), as well as RNA from S. aureus and S. epidermidis. However, only viable S. aureus were able to induce this response as these bacteria and not S. epidermidis were actively internalized by HaCaT. The stimulatory effect of S. aureus seems to be independent of the TLR3, -7 and -8 pathways.

Two cases of Hailey-Hailey disease effectively treated with apremilast and a review of reported cases

Hailey-Hailey disease (HHD) is an autosomal dominant genetic disease caused by a mutation of the ATP2C1 gene. Corticosteroids, antibiotics or cyclosporine have been administered to reduce inflammation and prevent flare-ups, but the efficacy is not always sufficient. We herein report two cases of HHD effectively treated with apremilast and review the previous literature. Patient 1 was a 28-year-old male and patient 2 was a 35-year-old female. Both patients were diagnosed with HHD based on histological and genetic analyses. Both patients were treated with oral antibiotics or topical corticosteroids, but their symptoms were refractory, therefore apremilast was administered to both patients. Two weeks later, the skin lesion of both patients was improved. No adverse reaction was observed except for mild headache in patient 2. There have been 13 reported cases of HHD treated with apremilast, including our cases. Eight cases showed a good response to apremilast, whereas five cases showed no response. There seems to be no association between the disease severity and efficacy of apremilast, although the reason remains unknown. Interestingly, an early improvement of the HHD lesion was observed in all good response cases. Although digestive symptoms, headache, and myalgia were observed as adverse events, the treatment was well-tolerated. The accumulation of a greater number of similar cases and further research will be required. We hypothesize that apremilast may be a useful therapeutic option for skin lesions of HHD.

Phenol-soluble modulins α are major virulence factors of Staphylococcus aureus secretome promoting inflammatory response in human epidermis

Staphylococcus aureus is a skin commensal microorganism commonly colonizing healthy humans. Nevertheless, S. aureus can also be responsible for cutaneous infections and contribute to flare-up of inflammatory skin diseases such as atopic dermatitis (AD), which is characterized by dysbiosis of the skin microbiota with S. aureus as the predominant species. However, the role of major virulence factors of this pathogen such as phenol-soluble modulin (PSM) toxins in epidermal inflammation remains poorly understood. Stimulation of primary human keratinocytes with sublytic concentrations of synthetic and purified PSM α3 resulted in upregulation of a large panel of pro-inflammatory chemokine and cytokine gene expression, including CXCL1, CXCL2, CXCL3, CXCL5, CXCL8, CCL20, IL-1α, IL-1β, IL-6, IL-36γ and TNF-α, while inducing the release of CXCL8, CCL20, TNF-α and IL-6. In addition, using S. aureus culture supernatant from mutants deleted from genes encoding either α-type PSMs or all PSM production, PSMs were shown to be the main factors of S. aureus secretome responsible for pro-inflammatory mediator induction in human keratinocytes. On the other hand, α-type PSM-containing supernatant triggered an intense induction of pro-inflammatory mediator expression and secretion during both topical and basal layer stimulation of an ex vivo model of human skin explants, a physiologically relevant model of pluristratified epidermis. Taken together, the results of this study show that PSMs and more specifically α-type PSMs are major virulence factors of S. aureus inducing a potent inflammatory response during infection of the human epidermis and could thereby contribute to AD flare-up through exacerbation of skin inflammation.

Plantaricin NC8 αβ prevents Staphylococcus aureus-mediated cytotoxicity and inflammatory responses of human keratinocytes

Multidrug resistance bacteria constitue an increasing global health problem and the development of novel therapeutic strategies to face this challenge is urgent. Antimicrobial peptides have been proven as potent agents against pathogenic bacteria shown by promising in vitro results. The aim of this study was to characterize the antimicrobial effects of PLNC8 αβ on cell signaling pathways and inflammatory responses of human keratinocytes infected with S. aureus. PLNC8 αβ did not affect the viability of human keratinocytes but upregulated several cytokines (IL-1β, IL-6, CXCL8), MMPs (MMP1, MMP2, MMP9, MMP10) and growth factors (VEGF and PDGF-AA), which are essential in cell regeneration. S. aureus induced the expression of several inflammatory mediators at the gene and protein level and PLNC8 αβ was able to significantly suppress these effects. Intracellular signaling events involved primarily c-Jun via JNK, c-Fos and NFκB, suggesting their essential role in the initiation of inflammatory responses in human keratinocytes. PLNC8 αβ was shown to modulate early keratinocyte responses, without affecting their viability. The peptides have high selectivity towards S. aureus and were efficient at eliminating the bacteria and counteracting their inflammatory and cytotoxic effects, alone and in combination with low concentrations of gentamicin. We propose that PLNC8 αβ may be developed to combat infections caused by Staphylococcus spp.

Neutrophil Recruitment to Noninvasive MRSA at the Stratum Corneum of Human Skin Mediates Transient Colonization

Staphylococcus aureus is a leading cause of skin and soft issue infection, but paradoxically, it also transiently, and often harmlessly, colonizes human skin. An obstacle to understanding this contradiction has been a shortage of in vivo models reproducing the unique structure and immunology of human skin. In this work, we developed a humanized model to study how healthy adult human skin responds to colonizing methicillin-resistant S. aureus (MRSA). We demonstrate the importance of the outer stratum corneum as the major site of bacterial colonization and how noninvasive MRSA adhesion to corneocytes induces a local inflammatory response in underlying skin layers. This signaling recruits neutrophils to the skin, where they control bacterial numbers, mediating transiency in colonization. This work highlights the spatiotemporal aspects of human skin colonization and demonstrates a subclinical inflammatory response to noninvasive MRSA that allows human skin to regulate the bacterial population at its outer surface.

Tissue microenvironment initiates an immune response to structural components of Staphylococcus aureus

Cell-to-cell communication in skin participates to the maintenance of homeostatic responses to foreign substances. Certain strains of Staphylococcus (S) aureus are vicious pathogens that cause deleterious effects in host cells and tissues. Both secreted toxins and structural components of S. aureus trigger an immune response, though how S. aureus stimulates host immune responses is poorly understood. We explored here how keratinocytes and fibroblasts initiate the first steps of an immune response by activating dendritic cells (DCs) through recognition of structural components of S. aureus. We treated monocyte-derived Langerhans cells (moLCs) and monocyte-derived DCs (moDCs) with conditioned media from keratinocytes (K-CM) and fibroblasts (F-CM) treated with heat-killed S. aureus (HKSA) respectively, or directly with HKSA. Immune and inflammatory responses from keratinocytes, fibroblasts, moLCs and moDCs were assessed by analysis of cell surface markers and cytokine production using flow cytometry, real-time PCR and ELISA assays. K-CM and F-CM increased the expression of CD86 and HLA-DR on moLCs and moDCs, in association with a specific cytokine profile. K-CM upregulated TNFA, IL-1B and GM-CSF mRNA expression in moLCs, while F-CM upregulated IL-12 and downregulated TNFA and TGFB mRNA expression in moDCs. Additionally, F-CM attenuated the induction of an inflammatory profile in monocytes. The recognition of structural components from S. aureus by cutaneous microenvironment induces the activation and the expression of specific cytokines from LCs and DCs.

A canine keratinocyte cell line expresses antimicrobial peptide and cytokine genes upon stimulation with bacteria, microbial ligands and recombinant cytokines

Keratinocytes (KC) are the main cellular components of the stratum corneum that constitutes a solid physical skin barrier representing the first line of defense against pathogens. Moreover, KC are potent producers of inflammatory mediators and antimicrobial peptides (AMP) when activated through their pattern recognition receptors. In atopic dermatitis (AD) the protective skin barrier may be compromised due to barrier disruption, secondary infection and accelerated secretion of inflammatory cytokines which may also affect AMP expression in the skin. In the present study, we addressed the responses of a canine KC cell line upon exposure to Staphylococcus pseudintermedius, typically found on canine atopic skin during secondary infections, and stimulation by individual AD-associated ligands and cytokines. All stimuli induced a significant increase in expression of the pro-inflammatory cytokine genes tumor necrosis factor (TNF)-α and interleukin (IL)-8, but with different kinetics. Limited effects were observed on AMP gene expression except for K9CATH which was significantly upregulated upon bacterial infection but with none of the individual AD-associated ligands. Interestingly, K9CATH possessed antimicrobial activity towards Staphylococcus pseudintermedius, indicating that K9CATH expression is a specific defense reaction towards bacterial infection and not part of a general pro-inflammatory profile of KC.

Thymol attenuates the worsening of atopic dermatitis induced by Staphylococcus aureus membrane vesicles

Staphylococcus aureus membrane vesicles (MVs) aggravate atopic dermatitis (AD) through the delivery of bacterial effector molecules to host cells and the stimulation of inflammatory responses. This study investigated the inhibitory effect of thymol, a phenolic monoterpene found in essential oils derived from plants, on the worsening of AD induced by S. aureus MVs both in vitro and in vivo. The sub-minimal inhibitory concentrations of thymol disrupted S. aureus MVs. Intact S. aureus MVs induced the expression of pro-inflammatory cytokine (interleukin (IL)-1β, IL-6, and tumor necrosis factor-α) and chemokine (IL-8 and monocyte chemoattractant protein-1) genes in cultured keratinocytes, whereas thymol-treated S. aureus MVs did not stimulate the expression of these genes. Topical application of thymol-treated S. aureus MVs or treatment with thymol after intact S. aureus MVs to AD-like skin lesions diminished the pathology of AD. This included decreases in epidermal/dermal thickness and infiltration of eosinophils/mast cells, and inhibited expression of pro-inflammatory cytokine and chemokine genes in mouse AD model. Moreover, thymol significantly suppressed the Th1, Th2, and Th17-mediated inflammatory responses in AD-like skin lesions induced by S. aureus MVs, and reduced the serum levels of immunoglobulin (Ig) G2a, mite-specific IgE, and total IgE. In summary, thymol disrupts S. aureus MVs and suppresses inflammatory responses in AD-like skin lesions aggravated by S. aureus MVs. Our results suggest that thymol is a possible candidate for the management of AD aggravation induced by S. aureus colonization or infection in the lesions.

Epic Immune Battles of History: Neutrophils vs. Staphylococcus aureus

Neutrophils are the most abundant leukocytes in human blood and the first line of defense after bacteria have breached the epithelial barriers. After migration to a site of infection, neutrophils engage and expose invading microorganisms to antimicrobial peptides and proteins, as well as reactive oxygen species, as part of their bactericidal arsenal. Ideally, neutrophils ingest bacteria to prevent damage to surrounding cells and tissues, kill invading microorganisms with antimicrobial mechanisms, undergo programmed cell death to minimize inflammation, and are cleared away by macrophages. Staphylococcus aureus (S. aureus) is a prevalent Gram-positive bacterium that is a common commensal and causes a wide range of diseases from skin infections to endocarditis. Since its discovery, S. aureus has been a formidable neutrophil foe that has challenged the efficacy of this professional assassin. Indeed, proper clearance of S. aureus by neutrophils is essential to positive infection outcome, and S. aureus has developed mechanisms to evade neutrophil killing. Herein, we will review mechanisms used by S. aureus to modulate and evade neutrophil bactericidal mechanisms including priming, activation, chemotaxis, production of reactive oxygen species, and resolution of infection. We will also highlight how S. aureus uses sensory/regulatory systems to tailor production of virulence factors specifically to the triggering signal, e.g., neutrophils and defensins. To conclude, we will provide an overview of therapeutic approaches that may potentially enhance neutrophil antimicrobial functions.

Medium dose ultraviolet A1 phototherapy and mRNA expression of interleukin 8, interferon γ, and chemokine receptor 4 in acute skin lesions in atopic dermatitis

Introduction

Mechanisms responsible for UVA1 efficacy in atopic dermatitis (AD) are not fully elucidated.

Aim

To investigate IL-8, CCR-4, and IFN-γ mRNA expression in AD before and after UVA1, to identify correlations among them, and to determine whether and to what degree mRNA expression is influenced by UVA1.

Material and methods

Twenty-five patients with AD underwent medium dose UVA1-phototherapy at daily dosages of 10, 20, 30, 45, and then continuing 45 J/cm² up to 20 days, from Monday to Friday for 4 weeks. Before and after UVA1, biopsies from acute skin lesions were studied using reverse-transcription and RT-PCR.

Results

The levels of CCR-4 mRNA correlated with those of IFN-γ, both before and after UVA1 phototherapy (p < 0.05). A significant correlation was found after UVA1 between mRNA levels of IL-8 and IFN-γ (p < 0.05). After UVA1 an increase in IL-8 mRNA expression in comparison to the baseline assessment (p = 0.02) was found, while no significant difference was revealed in the expression of CCR-4 and IFN-γ mRNA. UVA1 improved both SCORAD and severity of AD (p < 0.001). SCORAD and the severity of AD did not correlate with the degree of expression of measured cytokine mRNA, neither before nor after UVA1.

Conclusions

CCR-4 is expressed in parallel with IFN-γ in acute skin lesions of patients with AD both before and after UVA1 phototherapy. UVA1 significantly improves SCORAD index, lessens the severity of AD and increases the expression of IL-8, with no direct effects on other studied molecules.

Staphlyococcus aureus phenol-soluble modulins stimulate the release of proinflammatory cytokines from keratinocytes and are required for induction of skin inflammation

Staphylococcus aureus is a human commensal that colonizes the skin. While it is normally innocuous, it has strong associations with atopic dermatitis pathogenesis and has become the leading cause of skin and soft tissue infections in the United States. The factors that dictate the role of S. aureus in disease are still being determined. In this work, we utilized primary keratinocyte culture and an epidermal murine colonization model to investigate the role of S. aureus phenol-soluble modulins (PSMs) in proinflammatory cytokine release and inflammation induction. We demonstrated that many species of Staphylococcus are capable of causing release of interleukin 18 (IL-18) from keratinocytes and that S. aureus PSMs are necessary and sufficient to stimulate IL-18 release from keratinocytes independently of caspase 1. Further, after 7 days of epicutaneous exposure to wild-type S. aureus, but not S. aureus Δpsm, we saw dramatic changes in gross pathology, as well as systemic release of proinflammatory cytokines. This work demonstrates the importance of PSM peptides in S. aureus-mediated inflammatory cytokine release from keratinocytes in vitro and in vivo and further implicates PSMs as important contributors to pathogenesis.

Cutaneous innate immune sensing of Toll-like receptor 2-6 ligands suppresses T cell immunity by inducing myeloid-derived suppressor cells

Skin is constantly exposed to bacteria and antigens, and cutaneous innate immune sensing orchestrates adaptive immune responses. In its absence, skin pathogens can expand, entering deeper tissues and leading to life-threatening infectious diseases. To characterize skin-driven immunity better, we applied living bacteria, defined lipopeptides, and antigens cutaneously. We found suppression of immune responses due to cutaneous infection with Gram-positive S. aureus, which was based on bacterial lipopeptides. Skin exposure to Toll-like receptor (TLR)2-6-binding lipopeptides, but not TLR2-1-binding lipopeptides, potently suppressed immune responses through induction of Gr1(+)CD11b(+) myeloid-derived suppressor cells (MDSCs). Investigating human atopic dermatitis, in which Gram-positive bacteria accumulate, we detected high MDSC amounts in blood and skin. TLR2 activation in skin resident cells triggered interleukin-6 (IL-6), which induced suppressive MDSCs, which are then recruited to the skin suppressing T cell-mediated recall responses such as dermatitis. Thus, cutaneous bacteria can negatively regulate skin-driven immune responses by inducing MDSCs via TLR2-6 activation.

Salivary epithelial cells as model to study immune response against cutaneous pathogens

The human skin not only provides passive protection as a physical barrier against external injury, but also mediates active surveillance via epidermal cell surface receptors that recognize and respond to potential invaders. Primary keratinocytes and immortalized cell lines, the commonly used sources to investigate immune responses of cutaneous epithelium are often difficult to obtain and/or potentially exhibit changes in cellular genetic make-up. Here we investigated the possibility of using salivary epithelial cells (SEC) to evaluate the host response to cutaneous microbes. Elevated secretion of IFN-γ and IL-12 was observed in the SEC stimulated with Staphylococcus aureus, a transient pathogen of the skin, as mono species biofilm as compared to SEC stimulated with a commensal microbe, the Staphylococcus epidermidis. Co-culture of the SEC with both microbes as dual species biofilm elicited maximum cytokine response. Stimulation with S. aureus alone but not with S. epidermidis alone induced maximum toll-like receptor-2 (TLR-2) expression in the SEC. Exposure to dual species biofilm induced a sustained upregulation of TLR-2 in the SEC for up to an hour. The data support novel application of the SEC as efficient biospecimen that may be used to investigate personalized response to cutaneous microflora.

Effect of poly-L-lysine-chlorin P6-mediated antimicrobial photodynamic treatment on collagen restoration in bacteria-infected wounds

OBJECTIVE

The purpose of this work was to study the effect of poly-L-lysine-conjugated chlorin P6 (pl-cp6)-mediated antimicrobial photodynamic treatment (APDT) on collagen remodeling of murine excisional wounds infected with methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO).

BACKGROUND DATA

Bacterial infection of wounds leads to compromised collagen remodelling. APDT-induced inactivation of bacteria and bacterial proteases are expected to restore collagen remodeling in wounds. However, published reports on the effect of PDT on wound healing are somewhat contradictory. One of the reasons for these observations could be the random sampling of wound repair outcomes by invasive technques such as histology.

METHODS

Post-wounding time-dependent changes in collagen restoration were monitored noninvasively using polarization sensitive optical coherence tomography (PSOCT) and compared with histology and hydroxyproline level. Immunoblotting was performed to study matrix metalloproteinase (MMP) level.

RESULTS

As indicated by retardance measurements from PSOCT images and immunoblotting, bacteria-infected wounds showed slower collagen restoration and higher MMP-8, 9 expression, than did uninfected wounds. In contrast, in infected wounds treated with pl-cp6 and light, retardance was higher (approximately twofold) compared with wounds treated with pl-cp6 alone. These results were consistent with lower MMP-8, 9 level on day 5, more ordered collagen matrix, and higher hydroxyproline content (approximately threefold) on day 18, observed in photodynamically treated wounds, compared with that of untreated infected wounds.

CONCLUSIONS

APDT expedites healing in bacteria-infected wounds in mice by attenuating collagen degradation and by enhancing epithelialization, hydroxyproline content, and collagen remodelling.

Staphylococcus aureus inhibits terminal differentiation of normal human keratinocytes by stimulating interleukin-6 secretion

BACKGROUND

Staphylococcus aureus (S. aureus) is found on the skin of approximately 90% of patients with atopic dermatitis and approximately 20% of apparently healthy subjects. S. aureus induces keratinocytes and immune cells to secrete immunoregulatory factors that cause epidermal barrier dysfunction in atopic skin.

OBJECTIVE

This study examined factors that cause epidermal permeability barrier dysfunction in skin colonized by S. aureus.

METHODS

We examined the effect of S. aureus on keratinocyte differentiation in the stratum corneum (SC) of in vivo skin, normal human keratinocytes (NHKs) and a reconstructed human epidermis (RHE) model. The fold change in expression of the terminal differentiation markers and the level of secreted cytokines were investigated.

RESULTS

The SC displayed decreased expression of keratin 10 (KRT 10). NHKs treated with S. aureus extracts increased expression of interleukin (IL)-6 and significantly reduced expression of the terminal differentiation markers KRT 1, KRT 10, loricrin (LOR), and filaggrin (FLG); however, the expression of basal layer markers (KRT 5, KRT 14) remained unchanged. Treatment of NHKs with an anti-IL-6 antibody in combination with IL-6 or the S. aureus extracts inhibited the decrease in KRT 10 mRNA or protein expression. After the RHEs were exposed to the S. aureus extracts, KRT 1 and KRT 10 protein levels decreased.

CONCLUSIONS

These findings suggest that S. aureus inhibits the terminal differentiation of keratinocytes by stimulating IL-6 secretion.

Inflammatory and antimicrobial responses to methicillin-resistant Staphylococcus aureus in an in vitro wound infection model

Treatment of patients with burn wound infections may become complicated by the presence of antibiotic resistant bacteria and biofilms. Herein, we demonstrate an in vitro thermal wound infection model using human skin equivalents (HSE) and biofilm-forming methicillin-resistant Staphylococcus aureus (MRSA) for the testing of agents to combat such infections. Application of a liquid nitrogen-cooled metal device on HSE produced reproducible wounds characterized by keratinocyte death, detachment of the epidermal layer from the dermis, and re-epithelialization. Thermal wounding was accompanied by up-regulation of markers for keratinocyte activation, inflammation, and antimicrobial responses. Exposure of thermal wounded HSEs to MRSA resulted in significant numbers of adherent MRSA/HSE after 1 hour, and multiplication of these bacteria over 24-48 hours. Exposure to MRSA enhanced expression of inflammatory mediators such as TLR2 (but not TLR3), IL-6 and IL-8, and antimicrobial proteins human β-defensin-2, -3 and RNAse7 by thermal wounded as compared to control HSEs. Moreover, locally applied mupirocin effectively reduced MRSA counts on (thermal wounded) HSEs by more than 99.9% within 24 hours. Together, these data indicate that this thermal wound infection model is a promising tool to study the initial phase of wound colonization and infection, and to assess local effects of candidate antimicrobial agents.

Dendritic cells produce inflammatory cytokines in response to bacterial products from Staphylococcus aureus-infected atopic dermatitis lesions

Atopic Dermatitis (AD) patients often acquire secondary skin infections resulting in increased inflammation. The increased inflammation occurs through the activation of multiple cell types including dendritic cells (DC). In this study, we investigated the activity of soluble products present in infected AD lesions by measuring the ability of patients' wash fluids from a quantitative culture of lesions to activate DC. We found that wash fluid derived from AD lesions induced cytokine production by murine bone marrow-derived DC, including IL-1β, IL-6, ΙL-10, and tumor necrosis factor-α. The lipoprotein lipoteichoic acid (LTA) from Staphylococcusaureus was implicated as a potent stimulus in the wash fluids as only wash fluid samples that contained LTA exerted this activity, and exogenous LTA triggered similar DC cytokine activation. Wash fluid- and LTA-stimulated DC cytokine production required MyD88, but not the platelet-activating factor receptor (PAF-R), despite the ability of LTA to function through this receptor in keratinocytes. Thus, our results support a role for DC in the worsening of AD inflammation due to secondary bacteria infections.

Staphylococcus aureus stimulates neutrophil targeting chemokine expression in keratinocytes through an autocrine IL-1alpha signaling loop

Staphylococcus aureus is a significant human pathogen that can colonize the skin. Neutrophils are well known to be involved in clearance of the bacterium. This study focused on exploring the role that human keratinocytes have as first responders to bacterial challenges. IL-1alpha and IL-1beta increased mRNA production and protein secretion of the neutrophil chemotactic CXCL1, CXCL2, and IL-8 in keratinocytes. S. aureus and the bacterial cell wall components lipoteichoic acid (LTA) and peptidoglycan (PGN) induced similar expression profiles in a Toll-like receptor (TLR)-2-dependent manner. Interestingly, the S. aureus-induced mRNA levels peaked at later time points than those induced by IL-1. The S. aureus-activated chemokine production was preceded by significant IL-1alpha and IL-1beta secretion. Expression of IL-1alpha was significantly higher than that of IL-1beta. Inhibition of IL-1RI using neutralizing antibodies revealed that S. aureus-derived LTA and PGN-induced chemokine expression requires IL-1RI engagement. Surprisingly, we further found that chemokine secretion is dependent upon endocrine IL-1alpha, but not IL-1beta, signaling. Our data show that the innate immune response of keratinocytes is regulated differently than those of other cell types. This may represent a fail-safe system that protects the host against genetic variation and immune evasion mechanisms developed by pathogens.

Effects of 15-deoxy-∆¹²,¹⁴-prostaglandin J₂ on the production of IL-8 and the expression of Toll-like receptor 2 in human primary keratinocytes stimulated with lipopolysaccharide

15-deoxy-∆(12,14)-prostaglandin J(2) (15d-PGJ(2)) is an anti-inflammatory prostaglandin that plays a role in promoting the resolution of inflammation. We investigated the effects of 15d-PGJ(2) on the production of IL-8 and on the expression of Toll-like receptors (TLRs) 2 in human primary keratinocytes stimulated with lipopolysaccharide (LPS). Cell proliferation was analyzed using the MTT assay, TLR2 and -4 mRNA expression was detected by RT-PCR, and IL-8 production and NF-κB p65 activities were determined by ELISA. LPS and 15d-PGJ(2) did not influence the proliferation rate at low concentrations (0.5 and 2.0 μM) in keratinocytes, and showed toxicity at high concentrations (5.0 μM). LPS, compared with control, induced the expression of TLR2 mRNA, increased IL-8 production, and enhanced NF-κB activity. 15d-PGJ(2) decreased TLR2 mRNA, increased IL-8 production, and suppressed NF-κB activity. Costimulation with LPS and 15d-PGJ(2), compared with LPS stimulation alone, decreased TLR2 mRNA (1.8-fold), increased IL-8 production (1.8-fold at 0.5 μM and 3.7-fold at 2.0 μM), and inhibited NF-κB activity (3.3-fold at 0.5 μM and 5.1-fold at 2.0 μM). TLR4 mRNA was not expressed in primary keratinocytes. These results suggest that 15d-PGJ(2) suppresses TLR2 expression and that it up-regulates the production of IL-8 by inhibiting the NF-κB signaling pathway in primary keratinocytes. Thus, 15d-PGJ(2) can have both anti- and pro-inflammatory effects, and 15d-PGJ(2)-mediated IL-8 up-regulation is related to the mitogen-activated protein kinase (MAPK) and NF-κB signaling pathways.

Infected atopic dermatitis lesions contain pharmacologic amounts of lipoteichoic acid

BACKGROUND

Bacterial infection with Staphylococcus aureus is a known trigger for worsening of atopic dermatitis (AD); the exact mechanisms by which bacterial infection worsens dermatitis are unknown.

OBJECTIVE

We sought to characterize the amounts of the biologically active bacterial lipoprotein lipoteichoic acid (LTA) in infected AD lesions.

METHODS

Eighty-nine children with clinically impetiginized lesions of AD were enrolled in this study. A lesion was graded clinically by using the Eczema Area and Severity Index (EASI), wash fluid obtained from the lesion for quantitative bacterial culture, and measurement of LTA and cytokines. The staphylococcal isolate was tested for antibiotic susceptibilities. The patients were treated with a regimen that included topical corticosteroids and systemic antibiotics, and the lesion was reanalyzed after 2 weeks.

RESULTS

S aureus was identified in 79 of 89 children enrolled in the study. The bacterial colony-forming unit (CFU) counts correlated with the EASI lesional score (P = .04). LTA levels as high as 9.8 mug/mL were measured in the wash fluid samples, and the amounts correlated with the lesional EASI scores (P = .01) and S aureus CFU (P < .001). Approximately 30% of clinically impetiginized AD lesions contained greater than 1 mug/mL LTA, amounts that exert effects on various cell types in vitro. Moreover, injection of skin tissue ex vivo with amounts of LTA found in AD lesions resulted in epidermal cytokine gene expression.

CONCLUSION

Pharmacologic levels of LTA are found in many infected atopic dermatitis lesions.

Development of three-dimensional tissue-engineered models of bacterial infected human skin wounds

While infected skin wounds are on the increase because of ageing populations, rising incidence of diabetes, and antibiotic resistance, we lack relevant in vivo or in vitro models to study many aspects of bacterial interaction with skin. The aim of this study was to develop three-dimensional models of normal human skin to study bacterial infection. The common dermatological pathogens Staphylococcus aureus and Pseudomonas aeruginosa were used to infect tissue-engineered skin, and the course of infection in the skin was examined over several days. Two forms of model were developed-one in which bacteria were introduced directly to 10 mm wounds in the epidermis, and another in which wounds were created by burning a 4 mm hole in the center of the tissue before inoculation. The bacteria flourished within the engineered skin, and colonized the upper epidermal layers before invasion into the dermis. Infection with P. aeruginosa caused a loss of epidermis and de-keratinization of the skin constructs, as well as partial loss of basement membrane. These novel complex human skin infection models could be used to investigate microbial invasion of normal skin epithelium, basement membrane, and connective tissue, and as a model to study approaches to reduce bacterial burden in skin wounds.

NOD2 contributes to cutaneous defense against Staphylococcus aureus through alpha-toxin-dependent innate immune activation

Staphylococcus aureus is a major cause of community-acquired and nosocomial infections including the life-threatening conditions endocarditis, necrotizing pneumonia, necrotizing fasciitis, and septicemia. Toll-like receptor (TLR)-2, a membrane-bound microbial sensor, detects staphylococcal components, but macrophages lacking TLR2 or both TLR2 and TLR4 remain S. aureus responsive, suggesting that an alternative microbial recognition receptor might be involved. The cytoplasmic sensor nucleotide-binding oligomerization domain containing (NOD) 2/caspase recruitment domain (CARD) 15 detects muramyl dipeptide from bacterial peptidoglycans and mediates cytokine responses to S. aureus in vitro, but the physiological significance of these observations is not well defined. Here we show that NOD2-deficient mice exhibit a delayed but ultimately exacerbated ulcerative response and impaired bacterial clearance after s.c. infection with S. aureus. NOD2-dependent recognition of S. aureus and muramyl dipeptide is facilitated by alpha-toxin (alpha-hemolysin), a pore-forming toxin and virulence factor of the pathogen. The action of NOD2 is dependent on IL-1beta-amplified production of IL-6, which promotes rapid bacterial killing by neutrophils. These results significantly broaden the physiological importance of NOD2 in innate immunity from the recognition of bacteria that primarily enter the cytoplasm to the detection of bacteria that typically reside extracellularly and demonstrate that this microbial sensor contributes to the discrimination between commensal bacteria and bacterial pathogens that elaborate pore-forming toxins.

Interplay among oxidants, antioxidants, and cytokines in skin disorders: Present status and future considerations

The pathogenicity of skin disorders involves a complexity of physiological, immunological, environmental, and genetic phenomena. This review focuses on cross-talks between two main agents, the oxidants and cytokines network, which have recently been found to play important roles in the pathophysiology of a large variety of skin disorders, including carcinogenesis, UVB irradiation damages, inflammatory processes, and a series of diseases such as, psoriasis, pyoderma gangrenosum, atopic dermatitis, irritant contact dermatitis, and bacterial skin infections. In particular the review discusses the question how an interplay between oxidants and cytokines might be beneficial in wound-healing and in therapeutic strategies in clinical settings. These involve topical applications and oral administration of antioxidant and inflammatory-cytokines-neutralizing antibodies. Monitoring cytokine expression in skin disorders (inflammatory versus anti-inflammatory, or Th1 versus Th2 types of cytokines) will definitely help to evaluate the severity of injury, its type, and its role in therapy. Furthermore, it is expected that future studies should explore the possible roles of the synergistic interactions between antioxidants and cytokines and their impact on the Th1/Th2 cytokine networks balances.

Effect of matrine on the expression of substance P receptor and inflammatory cytokines production in human skin keratinocytes and fibroblasts

Matrine is a kind of alkaloid found in certain Sophora plants, which has been extensively used in China for the treatment of viral hepatitis, cancer, cardiac diseases and skin diseases (such as atopic dermatitis and eczema). It also has been confirmed that substance P (SP) and its receptor (neurokinin-1 receptor, NK-1R) are involved in the pathogenesis of inflammatory skin disorders. So the present study was designed to investigate the effect of matrine on the expression of NK-1R and cytokines production induced by SP in HaCaT cells (a human epidermal keratinocyte cell line) and dermal fibroblasts. In addition, cell viability was also evaluated. The results showed that matrine inhibited the expression of NK-1R in HaCaT cells and fibroblasts. SP induced the production of interleukin (IL)-1beta, IL-8, interferon (IFN)-gamma, and monocyte chemotactic protein (MCP)-1 in both cell types. Matrine 5-100 microg/mL had little effect on cell viability. It inhibited SP-induced IL-1beta, IL-8 and MCP-1 production in HaCaT cells and fibroblasts, while it increased the production of IFN-gamma in HaCaT cells. Both SP and matrine had no effect on the secretion of IL-6. These findings suggest that matrine may have potential treatment function on SP related cutaneous inflammation by inhibition of the expression of substance P receptor and regulation of the production of inflammatory cytokines.

Effects of the neuropeptides substance P, calcitonin gene-related peptide, vasoactive intestinal polypeptide and galanin on the production of nerve growth factor and inflammatory cytokines in cultured human keratinocytes

Neuropeptides released from the cutaneous sensory nerve endings have neurotransmitter and immunoregulatory roles; they exert mitogenic actions and can influence the functions of different cell types in the skin. The aims of this study were a systematic investigation of the effects of the neuropeptides substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP) and galanin (GAL) on the inflammatory cytokine production (IL-1alpha, IL-8 and TNF-alpha) of the keratinocytes, and a study of their role in the production and secretion of nerve growth factor (NGF) and its precursor molecule (proNGF). Cultures of normal human keratinocytes were treated with 10(-8)M SP, CGRP, VIP or GAL for 30 min. After different time intervals, cells were harvested for total RNA isolation; in addition, cell lysates and supernatants were collected. The effects of the neuropeptides on the mRNA expressions of the different cytokines and NGF were investigated by Q-RT-PCR and the protein levels were studied by means of ELISA assays and Western blotting. Each of the four neuropeptides induced increases in the expressions of IL-1alpha, IL-8 and TNF-alpha mRNA. Increases appeared in the amount of the IL-1alpha protein in the supernatants of neuropeptide-treated cells, and the IL-8 secretion was mildly elevated, while secretion of TNF-alpha remained undetectable. The four neuropeptides increased the NGF mRNA expression to different extents. In the cell lysates of the keratinocytes, only proNGF could be detected, its concentration in the neuropeptide-treated cells being approximately twice that in the time-matched controls. Both control cultures and neuropeptide-treated cultures were found to secrete proNGF and mature NGF, but neuropeptide-treated cell cultures produced markedly higher (3-7-fold) amounts of NGF-like immunoreactive materials. The results demonstrated that neuropeptides released from cutaneous nerves after an injurious stimulus are able to induce an upregulation of IL-1alpha and IL-8 production; they are additionally able to influence the expressions of proNGF/NGF and their secretion from the keratinocytes. These findings may contribute toward an understanding of the neural influence on skin health and disease.

Budesonide, but not tacrolimus, affects the immune functions of normal human keratinocytes

Topical immunosuppressant therapy is widely used in the treatment of inflammatory skin diseases such as psoriasis and atopic dermatitis. Besides its beneficial therapeutic effects, application of topical anti-inflammatory drugs may render the epidermis more vulnerable to invading pathogens by suppressing innate immune responses in keratinocytes, such as cytokine production and Toll-like receptor (TLR) expression. In order to evaluate and compare the immunosuppressive effects of different immunosuppressant drugs on keratinocytes, we treated lipopolysaccharide (LPS)-stimulated and -unstimulated normal human keratinocytes with the synthetic corticosteroid budesonide and the macrolide tacrolimus. The expressions of the pattern recognition receptors (PRRs) TLR2 and TLR4 were measured by quantitative RT-PCR, pro-inflammatory cytokines IL-1alpha, IL-8 and TNF-alpha were monitored by quantitative RT-PCR and by ELISA, and alterations in TLR2 protein level were measured by flow cytometry. Budesonide had a suppressive effect on both constitutive and LPS-induced IL-8 gene expression. The amount of TNF-alpha mRNA was diminished in unstimulated keratinocytes, while TLR2 mRNA expression was markedly enhanced both in unstimulated and LPS-treated cells after incubation with budesonide. This increase in TLR2 mRNA expression was also detectable at the protein level in LPS-stimulated cells. Tacrolimus had no effect on any of the examined genes. Budesonide, but not tacrolimus, significantly inhibited the NF-kappaB-dependent luciferase reporter activity in HaCaT cells after induction with LPS or TNF-alpha. Although tacrolimus and budesonide are both effective treatments in some inflammatory skin diseases, the data provided here imply differences in local therapeutic and adverse effects of these two topical immunosuppressants.

Microbial compounds induce the expression of pro-inflammatory cytokines, chemokines and human beta-defensin-2 in vaginal epithelial cells

Vaginal epithelium has a powerful innate immune system that protects the female reproductive organs from bacterial and fungal infections. In the present study, we aimed to explore whether the Toll-like receptor (TLR) signaling pathway and the induction of pro-inflammatory cytokines and antimicrobial peptides could contribute to the protection against pathogenic microorganisms in vaginal epithelia, using an immortalized vaginal epithelial cell line PK E6/E7 as a model. We found that TLR2 and TLR4 receptors are expressed in vivo in the vaginal epithelia and in vitro in PK E6/E7 vaginal epithelial cell line. The Gram-negative cell wall compound lipopolysaccharide (LPS), the Gram-positive compound peptidoglycan (PGN), heat-killed Candida albicans and zymosan significantly (P<0.05) induced the expression of pro-inflammatory cytokines and chemokines such as TNF-alpha and IL-8/CXCL8 in vaginal epithelial cells. Furthermore, the expression and production of human beta-defensin-2 (hBD2), an antimicrobial peptide with chemotactic functions, was also up-regulated in PK E6/E7 cells after treatment with LPS, PGN or C. albicans. Treatment of vaginal epithelial cells with microbial compounds induced the activation and nuclear translocation of NF-kappaB transcription factor, a key element of innate and adaptive immune responses. In our work, we provide evidence that microbial compounds induce the production of pro-inflammatory cytokines, chemokines and antimicrobial peptides in vaginal epithelial cells. In vivo, vaginal epithelial cell-derived inflammatory mediators and antimicrobial peptides may play important roles in vaginal immune responses and in the elimination of pathogens from the female reproductive tract.

Alpha-MSH reduces the internalization of Staphylococcus aureus and down-regulates HSP 70, integrins and cytokine expression in human keratinocyte cell lines

Alpha-melanocyte-stimulating hormone (alpha-MSH) is a neuropeptide predominantly produced by the pituitary gland, but it is also generated by many extra-pituitary cells including keratinocytes of the skin. This neuropeptide has anti-inflammatory and antimicrobial effects and probably contributes in innate immunity. Staphylococcus aureus is the aetiological agent of a wide range of infections in humans. Colonization of human skin by S. aureus is a characteristic feature of several skin diseases and is often followed by tissue invasion and severe cell damage. The aim of our study was to detect a possible role of alpha-MSH during the early infection stages in the adhesion and penetration of keratinocytes before cell damage. Our data demonstrated that alpha-MSH precociously down-regulates the production of integrins such as beta1 and heat shock surface protein 70, essential molecules for the entry of S. aureus. Moreover, in our experimental model, alpha-MSH induces the down-regulation of the pro-inflammatory cytokine expression and of the adhesion molecules in keratinocytes activated by S. aureus. Our data suggest that alpha-MSH plays a protective role in the skin by reducing infection and the inflammatory process.

Bactericidal activity of flucloxacillin against Staphylococcus aureus in primary keratinocyte cultures of lesional and unaffected skin of patients suffering from atopic dermatitis

More than 90% of patients with atopic dermatitis (AD) are colonized by Staphylococcus aureus. Due to prevalent multi-resistant strains, it is highly difficult to eliminate S. aureus contamination of primary cell cultures of human AD skin by means of the antibiotics commonly used in cell culture. Therefore, an anti-staphylococcal treatment was investigated by which sterile proliferating keratinocyte cultures are attained from lesional and unaffected skin of AD patients by applying flucloxacillin, which in general is systemically used in vivo. The treatment with 1% flucloxacillin for 20 min included both colonized skin samples and contaminated primary cell cultures. In the case of persistent contamination, this step was repeated as often as required until complete decontamination without any cytotoxic indications was achieved. Antibacterial treatment with flucloxacillin permitted the cultivation of sterile, vital, and proliferating primary cultures of human skin keratinocytes from lesional and unaffected skin of AD patients with S. aureus colonization. The method increased the success rate of isolation of AD keratinocytes from 30 to 90%, representing on average 3 vs. 9 successfully isolated, sterile and proliferating cultures out of 10 contaminated skin biopsies, which is comparable to normal human keratinocyte isolation rates.