The interleukin-1 axis and cutaneous inflammation

Unraveling the Role of Sex Hormones on Keratinocyte Functions in Human Inflammatory Skin Diseases

The skin exerts several fundamental functions that are the first physical, chemical and immune barriers to the human body. Keratinocytes, the main cell type of the epidermis, provide mechanical defense, support skin integrity and actively endorse cutaneous immune responses. Not surprisingly, considering these crucial activities, alterations in keratinocyte functions are associated with different inflammatory skin diseases. Recent findings indicate that the skin should not only be regarded as a target for hormones but that it should also be considered as an endocrine peripheral organ that is directly involved in the synthesis and metabolism of these chemical messengers. Sex hormones have multiple effects on the skin, attributed to the binding with intracellular receptors expressed by different skin cell populations, including keratinocytes, that activate downstream signaling routes that modulate specific cellular functions and activities. This review is aimed at reorganizing the current knowledge on the role exerted by sex hormones on keratinocyte function in five different inflammatory skin diseases: Hidradenitis suppurativa; Acne vulgaris; Atopic dermatitis; progesterone hypersensitivity; psoriasis. The results of our work aim to provide a deeper insight into common cellular mechanisms and molecular effectors that might constitute putative targets to address for the development of specific therapeutic interventions.

Protective Effect of the Pearl extract from Pinctada fucata martensii Dunker on UV-induced Photoaging in Mice

Although the effect of pearl powder has been recognized for more than a thousand years from healthcare to beauty care, there has yet to be an in-depth understanding of its anti-photoaging effect. In the present study, the protective effect of pearl extract (PE) on UV-induced photoaging in mice was evaluated. First, the amino acid analysis of PE was carried out. Then, different dosages of pearl extract gel (PEG) were applied topically  on the shaved dorsal skins regions of mice before UV irradiation. Skin physiological and histological analysis, antioxidant enzymes and inflammatory factor test were used to evaluate the anti-photoaging effect of PEG. The results showed that PEG contained 14 amino acids, and could inhibit UV-irritated skin wrinkles, laxity, thickness, and dryness. Moreover, PEG upregulated the activities of CAT, GSH-Px, SOD and decreased MDA level, and suppressed the production of IL-1𝛽, IL-6, PGE 2 , TNF-𝛼, and COX-2 in UV-irradiated mice. The therapeutic effect in high dose PEG group was superior to those of positive control (Vitamin E). This study demonstrated the underlying mechanisms of PEG against UV-irritated photoaging. And PEG possesses a potential use in photoprotective medicines and cosmetics.

Anti-Aging Potential of Substance P-Based Hydrogel for Human Skin Longevity

Skin aging is generally caused by a decline in the components of the extracellular matrix (e.g., collagen and elastin) and due to inflammatory phenomena. Many growth factors and peptides with cell-growth and collagen-synthesis activities have shown promise in their application in anti-aging materials. However, the effect of collagen production, without anti-inflammatory effect, and skin penetration may not be enough for their use in anti-aging agents. Previously, we reported a substance P (SP)-based hydrogel (SP gel) that had potential wound-healing activities via induction of skin cell regeneration and collagen synthesis. Here, we analyzed the anti-aging activities and skin absorption effects of SP gel to extend its characterization. Toxicity tests, performed on human dermal fibroblasts (HDFs) and on a reconstructed 3D human skin model, indicated SP gel to be safe for long-term use, without causing irritation, even at high concentrations. In-vitro analysis revealed that SP gel elicited stronger collagen production activities than SP alone, and promoted anti-inflammatory effects with increased skin absorption properties. Moreover, SP gel did not induce melanin synthesis in a keratinocyte-melanocyte co-culture system. Together, the results suggest that SP gel has potential cosmetic effects and applicability as a novel ingredient in anti-aging products.

The Interplay Between Keratinocytes and Immune Cells in the Pathogenesis of Psoriasis

Psoriasis is a chronic inflammatory skin disease resulting from genetic, epigenetic, environmental, and lifestyle factors. To date, several immunopathogenic mechanisms of psoriasis have been elucidated, and, in the current model, the cross talk between autoreactive T cells and resident keratinocytes generates inflammatory and immune circuits responsible for the initiation, progression, and persistence of the disease. Several autoantigens derived from keratinocytes (i.e., LL37 cathelecidin/nucleic acid complexes, newly generated lipid antigens) have been identified, which may trigger initial activation of T cells, particularly IL-17-producing T cells, T helper (Th)1 and Th22 cells. Hence, lymphokines released in skin lesions are pivotal for keratinocyte activation and production of inflammatory molecules, which in turn lead to amplification of the local immune responses. Intrinsic genetic alterations of keratinocytes in the activation of signal transduction pathways dependent on T-cell-derived cytokines are also fundamental. The current review emphasizes the aberrant interplay of immune cells and skin-resident keratinocytes in establishing and sustaining inflammatory and immune responses in psoriasis.

Inflammaging in skin and other tissues - the roles of complement system and macrophage

Inflammaging refers to a continuous, low-grade inflammation associated with aging. Such chronic inflammatory response could build up with time and gradually causes tissue damage. It is considered as one of the driving forces for many age-related diseases such as diabetes, atherosclerosis, age-related macular degeneration (AMD), and skin aging. There is mounting evidence that indicates aging is driven by the pro-inflammatory cytokines and substances produced by our body’s innate immune system. The macrophage and complement system, two important components of innate immune system, have attracted more and more attention since they appear to be involved in the pathogenesis of several inflammaging-associated diseases, such as AMD and atherosclerosis. This paper will review what we know about these two innate immune systems in the pathogenesis of AMD, atherosclerosis and skin aging.

UVB radiation generates sunburn pain and affects skin by activating epidermal TRPV4 ion channels and triggering endothelin-1 signaling

At our body surface, the epidermis absorbs UV radiation. UV overexposure leads to sunburn with tissue injury and pain. To understand how, we focus on TRPV4, a nonselective cation channel highly expressed in epithelial skin cells and known to function in sensory transduction, a property shared with other transient receptor potential channels. We show that following UVB exposure mice with induced Trpv4 deletions, specifically in keratinocytes, are less sensitive to noxious thermal and mechanical stimuli than control animals. Exploring the mechanism, we find that epidermal TRPV4 orchestrates UVB-evoked skin tissue damage and increased expression of the proalgesic/algogenic mediator endothelin-1. In culture, UVB causes a direct, TRPV4-dependent Ca(2+) response in keratinocytes. In mice, topical treatment with a TRPV4-selective inhibitor decreases UVB-evoked pain behavior, epidermal tissue damage, and endothelin-1 expression. In humans, sunburn enhances epidermal expression of TRPV4 and endothelin-1, underscoring the potential of keratinocyte-derived TRPV4 as a therapeutic target for UVB-induced sunburn, in particular pain.

The role of cytokines in the pathomechanism of cutaneous disorders

Cytokines are produced transiently by cutaneous cells in response to immune stimuli. They are non-immunoglobulin proteins and glycoproteins. Cytokines, which are signaling molecules, act by sending downstream signals to various cells through a number of signal transduction pathways and by binding to cytokine receptors on the surface of cells. Cytokines regulate immunity and inflammation and thus play an important role in the pathogenesis of various cutaneous disorders.

IL-1 receptor signaling is required at multiple stages of sensitization and elicitation of the contact hypersensitivity response

Contact hypersensitivity (CHS) is a CD8 T cell-mediated response to hapten skin sensitization and challenge. The points at which IL-1R signaling is required during this complex, multistep immune response have not been clearly delineated. The role of IL-1R signaling during 2, 4 dinitro-1-fluorobenezene (DNFB) sensitization to induce hapten-specific CD8 effector T cells and in the trafficking of the effector T cells to the DNFB challenge site to elicit the response were investigated using IL-1R deficient mice. DNFB-sensitized IL-1R(-/-) mice had low CHS responses to hapten challenge that were caused in part by marked decreases in hapten-specific CD8 T cell development to IL-17- and IFN-γ-producing cells during sensitization. Hapten-primed wild type CD8 T cell transfer to naive IL-1R(-/-) mice did not result in T cell activation in response to hapten challenge, indicating a need for IL-1R signaling for the localization or activation, or both, of the CD8 T cells at the challenge site. Decreased CD8 T cell priming in sensitized IL-1R(-/-) mice was associated with marked decreases in hapten-presenting dendritic cell migration from the sensitized skin to draining lymph nodes. Transfer of hapten-presenting dendritic cells from wild type donors to naive IL-1R(-/-) mice resulted in decreased numbers of the dendritic cells in the draining lymph nodes and decreased priming of hapten-specific CD8 T cells compared with dendritic cell transfer to naive wild type recipients. These results indicate that IL-1R signaling is required at multiple steps during the course of sensitization and challenge to elicit CHS.

Immune functions of the skin

The skin, the body's largest organ, helps to secure the integrity of the host and, at the same time, allows the individual to communicate with the outside world. This finely tuned balance between protection from harmful pathogens (mostly microorganisms) and bidirectional signal exchange is provided by a network of structural, cellular, and molecular elements that are collectively referred to as the skin barrier. This "gateway" has a physical, chemical, and immunologic component. The role of the latter is to elicit a powerful defense reaction in the case of danger and, at the same time, to prevent such a reaction against innocuous substances. Immune responses originating in the skin are mounted and executed by cells and molecules of the innate or the adaptive immune system. Innate reactions are typically rapid, poorly discriminating, and do not exhibit memory. Adaptive responses, in contrast, show a high degree of specificity as well as memory but need a protracted time for their development. As a consequence, innate and adaptive responses are consecutive events influencing each other. In fact, we now know that the type and magnitude of the innate reactions govern and often determine the quality and quantity of adaptive responses.

Androgenetic alopecia in policemen: higher prevalence and different risk factors relative to the general population (KCIS no. 23)

Prevalence and risk factors of androgenetic alopecia (AGA) in policemen are not known. This study aimed to compare the prevalence and risk factors of AGA between policemen and the general population. A cross-sectional survey was conducted by recruiting a total of 758 (78%) of 972 policemen and 740 (80%) of 924 participants in a community-based integrated screening served as a comparison group. The Norwood classification system was used to assess the degree of hair loss. Information on age, family history of androgenetic alopecia, and other possible risk factors was collected with questionnaire interviews. The association analysis between policemen and the general population was limited to participants aged 40-59 years. After controlling for other significant factors, policemen aged 40-59 years had an increased risk of developing AGA compared with the general population (OR = 2.23, 95% CI 1.14, 4.36, p = 0.02). Obesity measured by waist circumference and body mass index made contribution to higher risk for AGA in younger policemen (20-39 years). A statistically significant association was noted between AGA and sunlight exposure in policemen aged 40-59 years. We concluded the prevalence of AGA in policemen was twofold higher than that in the general population. Obesity at young age and sunlight exposure may be responsible for higher risk of AGA in policemen. However, further studies are warranted to confirm the current findings.

IL-1 signalling determines the fate of skin grafts expressing non-self protein in keratinocytes

Although IL-1 is a known inflammatory cytokine during pathogen infection, the role of IL-1 in skin graft rejection, particularly where foreign antigen is expressed exclusively in keratinocytes, is less understood. Here, we use a syngeneic skin graft system, where antigens are expressed in epithelial cells via either a keratin 14 or keratin 5 promoter, to explore the role of IL-1 in graft rejection and induction of epithelial antigen-specific effector CD8(+) T-cell function. Keratin 5 ovalbumin (K5mOVA) transgenic skin grafts destined for rejection demonstrated increased expression of IL-1beta and its receptors compared to K14 HPV16 E7 transgenic grafts that do not reject spontaneously. Rejection of OVA grafts lacking the IL-1 receptor (IL-1R1) was delayed and associated with decreased numbers of antigen-specific CD8 T cells. In contrast, K14E7 grafts survived on immunocompetent, syngeneic recipients with decreased graft levels of IL-1beta and IL-1R1 and 2. However, in the absence of the IL-1 receptor antagonist, IL-1Ra, skin grafts were spontaneously rejected and an E7-specific CD8 T-cell response was primed. Thus, expression of the HPV16E7 oncoprotein in epithelial cells prevents IL-1beta-associated skin graft rejection and induction of antigen-specific CD8 T-cell responses. Enhancing IL-1beta signalling, via blocking of the IL-1 receptor antagonist, may represent an alternative strategy for treatment of HPV16E7-associated cancers.

Ultraviolet radiation and skin aging: roles of reactive oxygen species, inflammation and protease activation, and strategies for prevention of inflammation-induced matrix degradation - a review

Inflammation and the resulting accumulation of reactive oxygen species (ROS) play an important role in the intrinsic and photoaging of human skin in vivo. Environmental insults such as ultraviolet (UV) rays from sun, cigarette smoke exposure and pollutants, and the natural process of aging contribute to the generation of free radicals and ROS that stimulate the inflammatory process in the skin. UV irradiation initiates and activates a complex cascade of biochemical reactions in human skin. In short, UV causes depletion of cellular antioxidants and antioxidant enzymes (SOD, catalase), initiates DNA damage leading to the formation of thymidine dimmers, activates the neuroendocrine system leading to immunosuppression and release of neuroendocrine mediators, and causes increased synthesis and release of pro-inflammatory mediators from a variety of skin cells. The pro-inflammatory mediators increase the permeability of capillaries leading to infiltration and activation of neutrophils and other phagocytic cells into the skin. The net result of all these effects is inflammation and free radical generation (both reactive oxygen and nitrogen species). Furthermore, elastsases and other proteases (cathepsin G) released from neutrophils cause further inflammation, and activation of matrix metalloproteases. The inflammation further activates the transcription of various matrixes degrading metalloproteases, leading to abnormal matrix degradation and accumulation of non-functional matrix components. In addition, the inflammation and ROS cause oxidative damage to cellular proteins, lipids and carbohydrates, which accumulates in the dermal and epidermal compartments, contributing to the aetiology of photoaging. Strategies to prevent photodamage caused by this cascade of reactions initiated by UV include: prevention of UV penetration into skin by physical and chemical sunscreens, prevention/reduction of inflammation using anti-inflammatory compounds (e.g. cyclooxygenase inhibitors, inhibitors of cytokine generation); scavenging and quenching of ROS by antioxidants; inhibition of neutrophil elastase activity to prevent extracellular matrix damage and activation of matrix metalloproteases (MMPs), and inhibition of MMP expression (e.g. by retinoids) and activity (e.g. by natural and synthetic inhibitors).

Antifibrotic activity of an inhibitor of histone deacetylases in DOCA-salt hypertensive rats

BACKGROUND AND PURPOSE

Histone deacetylases (HDACs) silence genes by deacetylating lysine residues in histones and other proteins. HDAC inhibitors represent a new class of compounds with anti-inflammatory activity. This study investigated whether treatment with a broad spectrum HDAC inhibitor, suberoylanilide hydroxamic acid (SAHA), would prevent cardiac fibrosis, part of the cardiovascular remodelling in deoxycorticosterone acetate (DOCA)-salt rats.

EXPERIMENTAL APPROACH

Control and DOCA-salt rats were treated with SAHA (25 mg x kg(-1) x day(-1) s.c.) for 32 days. Changes in cardiovascular structure and function were assessed by blood pressure in vivo and in Langendorff perfused hearts, ventricular papillary muscle and in aortic rings in vitro. Left ventricular collagen deposition was assessed by histology.

KEY RESULTS

Administration of SAHA to DOCA-salt rats attenuated the following parameters: the increased concentration of over 20 pro-inflammatory cytokines in plasma, increased inflammatory cell infiltration and interstitial collagen deposition, increased passive diastolic stiffness in perfused hearts, prolongation of action potential duration at 20% and 90% of repolarization in papillary muscle, development of left ventricular hypertrophy, systolic hypertension and changes in vascular dysfunction.

CONCLUSIONS AND IMPLICATIONS

The HDAC inhibitor, SAHA, attenuated the cardiovascular remodelling associated with DOCA-salt hypertensive rats and improved cardiovascular structure and function, especially fibrosis, in the heart and blood vessels, possibly by suppressing inflammation. Control of cardiac histone or non-histone protein acetylation is a potential therapeutic approach to preventing cardiac remodelling, especially cardiac fibrosis.

Epidermal injury and infection during poxvirus immunization is crucial for the generation of highly protective T cell-mediated immunity

Variola major (smallpox) infection claimed hundreds of millions lives before it was eradicated by a simple vaccination strategy: epicutaneous application of the related orthopoxvirus vaccinia virus (VACV) to superficially injured skin (skin scarification, s.s.). However, the remarkable success of this strategy was attributed to the immunogenicity of VACV rather than to the unique mode of vaccine delivery. We now show that VACV immunization via s.s., but not conventional injection routes, is essential for the generation of superior T cell-mediated immune responses that provide complete protection against subsequent challenges, independent of neutralizing antibodies. Skin-resident effector memory T cells (T(EM) cells) provide complete protection against cutaneous challenge, whereas protection against lethal respiratory challenge requires both respiratory mucosal T(EM) cells and central memory T cells (T(CM) cells). Vaccination with recombinant VACV (rVACV) expressing a tumor antigen was protective against tumor challenge only if delivered via the s.s. route; it was ineffective if delivered by hypodermic injection. The clinically safer nonreplicative modified vaccinia Ankara virus (MVA) also generated far superior protective immunity when delivered via the s.s. route compared to intramuscular (i.m.) injection as used in MVA clinical trials. Thus, delivery of rVACV-based vaccines, including MVA vaccines, through physically disrupted epidermis has clear-cut advantages over conventional vaccination via hypodermic injection.

Cytokine release and cytotoxicity in human keratinocytes induced by polycyclic aromatic hydrocarbons (1-methylpyrene and perylene)

The cytotoxic effects of two polycyclic aromatic hydrocarbons (PAH) (1-methyplyrene and perylene) were investigated on human skin keratinocytes. Normal human keratinocytes were cultured in the presence of various concentrations of 1-methylpyrene and perylene either alone or in combination. Following incubation, keratinocyte adhesion, viability, proliferation, colony-forming efficiency, and apoptosis/necrosis level were examined. The effects of PAH on wound healing were also determined in vitro using a scrape-wound healing assay on epidermis-like tissue. In addition, the inflammatory cell response to PAH insult was examined through interleukin-1 (IL-1) alpha and interleukin-6 (IL-6) secretion. Each individual PAH significantly decreased keratinocyte adhesion and viability in a concentration-dependent manner, which was associated with a reduced ability of keratinocytes to proliferate and form colonies. When PAH were combined, a greater effect on keratinocyte adhesion, viability, and proliferation was noted. Decreased cell proliferation/colony-forming efficiency was accompanied by increased cell apoptosis following incubation with either PAH. This effect was enhanced by the inhibitory influence on keratinocyte migration, as assessed by culture scratching. Each PAH also exerted a significant effect on keratinocyte immune functions by modulating the secretion of inflammatory mediators. Indeed, 1-methylpyrene or perylene, individually or when combined, significantly upregulated IL-1alpha and IL-6 secretion. This effect was greater and was concentration dependent when the PAH combination was used. Overall results indicate that 1-methylpyrene and perylene exerted a cytotoxic effect on human keratinocytes. Our findings may shed light on mechanisms underlying potential adverse effects of 1-methylpyrene and perylene on human skin.

Evaluation of EpiDerm full thickness-300 (EFT-300) as an in vitro model for skin irritation: studies on aliphatic hydrocarbons

The aim of this study was to understand the skin irritation effects of saturated aliphatic hydrocarbons (HCs), C9-C16, found jet fuels using in vitro 3-dimensional EpiDerm full thickness-300 (EFT-300) skin cultures. The EFT-300 cultures were treated with 2.5microl of HCs and the culture medium and skin samples were collected at 24 and 48h to measure the release of various inflammatory biomarkers (IL-1alpha, IL-6 and IL-8). To validate the in vitro results, in vivo skin irritation studies were carried out in hairless rats by measuring trans epidermal water loss (TEWL) and erythema following un-occlusive dermal exposure of HCs for 72h. The MTT tissue viability assay results with the EFT-300 tissue show that 2.5microl/tissue ( approximately 4.1microl/cm(2)) of the HCs did not induce any significant changes in the tissue viability for exposure times up to 48h of exposure. Microscopic observation of the EFT-300 cross-sections indicated that there were no obvious changes in the tissue morphology of the samples at 24h, but after 48h of exposure, tridecane, tetradecane and hexadecane produced a slight thickening and disruption of stratum corneum. Dermal exposures of C12-C16 HCs for 24h significantly increased the expression of IL-1alpha in the skin as well as in the culture medium. Similarly, dermal exposure of all HCs for 24h significantly increased the expression of interleukin-6 (IL-6) and IL-8 in the skin as well as in the culture medium in proportion to the HC chain length. As the exposure time increased to 48h, IL-6 concentrations increased 2-fold compared to the IL-6 values at 24h. The in vivo skin irritation data also showed that both TEWL and erythema scores increased with increased HCs chain length (C9-C16). In conclusion, the EFT-300 showed that the skin irritation profile of HCs was in the order of C9C10C11C12<C13 approximately C14 approximately C16 and that the tissue was an excellent in vitro model to predict in vivo irritation and to understand the structural activity relationship of HCs.

[Immunology of allergic contact dermatitis]

Eczema is one of the most common skin diseases in dermatological practice. The broad medical definition of eczema includes any acute but non-infectious inflammatory reaction of the skin. The relative homogeneity of both the clinical and histological manifestations of eczema is in stark contrast to the profound pathogenetic differences of its various forms. The group of contact dermatitis can be divided into two main categories: irritant and allergic. Irritant contact dermatitis is due to a principally non- immunological inflammatory reaction of the skin to various physical or chemical irritants. In sharp contrast, allergic contact dermatitis is an antigen-specific cellular immune response of the skin, which in general requires prior antigen-recognition and priming of immune cells. A comprehensive understanding of the complex interactions between immune cells, inflammatory mediators and adhesion molecules in the underlying pathogenesis of allergic contact dermatitis is key for a better functional understanding and the development of new therapeutic strategies.

Differential cytokine expression in skin after single and repeated irritation by sodium lauryl sulphate

In vivo levels of cytokines and presence of neutrophils and eosinophils in skin irritation are not well known. Our objective was to get more insight in inflammatory mediators and markers involved in single and repeated skin irritation. We sampled epidermis-derived fluid using a novel technology that includes application of a negative pressure on the skin after creation of micropores in the stratum corneum by a laser. In nine volunteers, transdermal fluid was sampled after a single 4-h 10% sodium lauryl sulphate exposure and a repeated 3-week exposure (0.1% sodium lauryl sulphate). Twenty-seven cytokines were assessed by multiplex assay, and IL-1alpha, eosinophil cationic protein and myeloperoxidase by enzyme-linked immunosorbent assay. Levels of eosinophil cationic protein were increased after irritation and correlated with levels of myeloperoxidase. The levels of inflammatory mediators showed large interindividual differences in unexposed and exposed skin. Despite this variation, several mediators clearly showed increased levels: CC chemokine ligand (CCL)11, CXCL10 and vascular endothelial growth factor after both single and repeated exposure, IL-1alpha and basic fibroblast growth factor after single exposure and interleukin-1 receptor antagonist (IL-1RA) after repeated exposure. After repeated exposure, CCL5 and the ratio IL-1RA/IL-1alpha both increased compared with single exposure. We conclude that single and repeated irritation induces differential and concerted expression of various inflammatory mediators and markers.

The psoriatic transcriptome closely resembles that induced by interleukin-1 in cultured keratinocytes: dominance of innate immune responses in psoriasis

Psoriasis has been considered an autoimmune, T cell-mediated disorder in which adaptive immune responses predominate over those of non-antigen-specific innate immunity. To test this hypothesis, we profiled the transcriptome of psoriatic tissue and compared the data with that from cultured human keratinocytes exposed to the proinflammatory cytokine interleukin (IL)-1alpha and the Th1 cytokine interferon-gamma. When compared with patient-matched, nonlesional skin biopsies, psoriatic samples exhibited regulation of 90 transcripts including several members of the epidermal differentiation complex, molecules with antimicrobial activity, and hyperproliferation-associated keratins. Stimulation of keratinocytes with interferon-gamma resulted in regulation of 252 transcripts, with particularly strong expression of the CXCR3-binding ligands CXCL9, -10, and -11 and class II major histocompatibility complex genes, primarily those of the HLA-DR and -DP families. In contrast, the transcriptome resulting from exposure of keratinocytes to IL-1alpha elicited differences in just 19 transcripts, particularly genes within the epidermal differentiation complex and antimicrobial molecules, including PI3 and DEFB4. Major differences between the two keratinocyte transcriptomes were exhibited with only five induced IL-1alpha transcripts also regulated in the interferon-gamma set. Unexpectedly, there was a high correlation between psoriatic lesional tissue and the IL-1alpha transcriptome. These findings suggest that the inflammatory milieu in the epidermal microenvironment in psoriasis is more likely dependent on evolutionarily ancient cytokines such as IL-1, rather than those of the adaptive immune response.

Determination of interleukin-1α in human NCTC 2544 keratinocyte cells as a predictor of skin irritation from lysine-based surfactants

Lysine derivative surfactants are a class of amino acid-based surfactants synthesized as lecithin analogues that deserve particular attention because of their low toxicity and high biocompatibility. To complete the toxicological profile of these surfactants, IL-1 alpha production (cell-associated and release to the culture medium) was determined as an in vitro method for predicting skin irritation. In addition, an MTT assay was used as a viability marker in keratinocytes NCTC 2544. Keratinocytes are a biologically relevant target for developing in vitro techniques to assess skin irritants: moreover, they are the principal source of the proinflammatory cytokine IL-1 alpha in the epidermis. Lysine derivatives proved to be less potent in stimulating IL-1 alpha synthesis and induced a lower release of this cytokine into the culture medium when compared to the anionic surfactant sodium dodecyl sulfate. Due to their low irritancy potential, lysine-based surfactants may offer promising applications in pharmaceutical and cosmetic preparations.

Analysis of interleukin-1β-modulated mRNA gene transcription in human gingival keratinocytes by epithelia-specific cDNA microarrays

BACKGROUND/OBJECTIVES

Proinflammatory cytokines such as interleukin-1beta are known to be synthesized in oral gingivitis and periodontitis and lead to the activation of the transcription factor nuclear factor-kappaB (NF-kappaB). Although numerous effects of interleukin-1beta on mesenchymal cells are known, e.g. up-regulation of intercellular adhesion molecule-1 in endothelial cells, little is known of the effects of interleukin-1beta on oral keratinocytes. The purpose of the present study was to seek interleukin-1beta-mediated alterations in mRNA gene transcription and a putative activation of NF-kappaB in oral gingival keratinocytes.

METHODS

As an in vitro model for gingivitis and periodontitis, immortalized human gingival keratinocytes (IHGK) were stimulated with the proinflammatory cytokine interleukin-1beta. An epithelia-specific cDNA microarray was used to analyze mRNA expression profiles from IHGK cells treated with 200 units interleukin-1beta/ml for 3, 6, 9, 12, and 24 h. Indirect immunofluorescence was carried out to detect NF-kappaB in IHGK following interleukin-1beta treatment.

RESULTS

Detailed analysis revealed distinct patterns of time-dependent changes, including genes induced or repressed early (3-6 h) or late (12-24 h) after interleukin-1beta treatment. Differentially expressed genes were involved in (i) cell stress, (ii) DNA repair, (iii) cell cycle and proliferation, (iv) anti-pathogen response, (v) extracellular matrix turnover, and (vi) angiogenesis. A large number of genes were responsive to NF-kappaB and induction was concomitant with nuclear translocation of the p65 RelA subunit of NF-kappaB. Interestingly, many of these genes contain multiple NF-kappaB binding sites in their promoters.

CONCLUSION

Analysis of altered gene expression allows identification of gene networks associated with inflammatory responses. In addition to a number of well-known genes involved in gingivitis and periodontitis, we identified novel candidates that might be associated with the onset and maintenance of an inflammatory disease.

Profiles of inflammatory cytokines following colorectal surgery: Relationship with wound healing and outcome

Inflammation is an essential component of normal wound healing. This study has correlated systemic (plasma) and local (wound fluid) concentrations of inflammatory cytokines (interleukin [IL]-6, tumor necrosis factor-alpha [TNF-alpha], and IL-1beta) with wound healing and surgical outcome following elective colorectal surgery. Paired plasma and wound fluid samples were collected (n = 44) postoperatively (days 1, 3, 5, 7) and analyzed by enzyme-linked immunosorbent assay (pg/mL). Cytokine levels were significantly greater in drain fluid than plasma on each postoperative day (POD); e.g., POD 1 : IL-6; drain fluid, median, 77,050 pg/mL (range 9,928-456,408); plasma, 241 pg/mL (22-1,333). Daily profiles of IL-6 and TNF-alpha were similar in drain fluid and plasma; IL-6 levels peaked on POD 1 decreasing to POD 7, and TNF-alpha levels increased from PODs 1 to 7. However, IL-1beta in plasma peaked on POD 1 and plateaued, whereas drain fluid showed two peaks (PODs 1 and 7). Only plasma levels of cytokines correlated to clinical parameters; IL-6 levels significantly correlated with postoperative complications; e.g., POD 5, complications 92(1-597) and no complications, 14(2-217). IL-6 also correlated with tumor pathology (Dukes stage, tumor depth, vascular invasion), and TNF-alpha levels correlated with the estimated blood loss during surgery. We conclude that local wound levels of cytokines correlated with the stage of wound healing, whereas systemic levels correlated with postoperative complications and tumor pathology.

Sympathetic nervous system influence on the innate immune response

Our studies focused on the sympathetic nervous system (SNS) influence on dendritic cells (DCs), which play a crucial role in the innate immune response. We found that DCs express a variety of adrenergic receptors (ARs) with alpha1-ARs playing a stimulatory and beta2-ARs an inhibitory effect on DCs migration. beta2-ARs in skin and bone marrow-derived DCs when stimulated by bacterial toll-like receptors (TLRs) agonists respond to norepinephrine (NE) by decreased interleukin-12 (IL-12) and increased IL-10 production which in turn downregulates inflammatory cytokine production and CCR7 expression and thus their migration ability leading to reduced T helper-1 (Th1) priming. We also found that contact sensitizers that may induce a predominant Th1 response, do so by inhibiting the local NE turnover in the skin. The SNS seems therefore to contribute in shaping the information conveyed by DCs to T cells and thus in inducing the appropriate adaptive immune response. In this sense, the SNS physiological influence may allow Th2 priming to fight infections sustained by extracellular pathogens and limit the risk for organ-specific autoimmune reactions associated with excessive Th1 priming and inhibition of T regulatory cell functions. More recently, we found that preconditioning of the skin by beta-adrenergic antagonist and the TLR2 agonist S. Aureus peptidoglycan (PGN) may instruct a Th1 adaptive response to a soluble protein antigen. On the contrary, when the TLR4 agonist E. Coli lipopolysaccharide was used, the presence of the beta-adrenergic antagonist was not effective. These effects were consonant with the pattern of TLRs expression shown by epidermal keratinocytes (EKs) but not by skin DCs. As beta-ARs signaling defects together with S. Aureus infections are thought to serve as initiation and/or persistence factors for numerous Th1-sustained autoimmune inflammatory skin diseases, we might have disclosed at least part of the relevant pathogenetic mechanism.

Rat epidermal keratinocyte organotypic culture (ROC) as a model for chemically induced skin irritation testing

The potential of rat epidermal keratinocyte (REK) organotypic culture (ROC) with proper stratum corneum barrier as a model for screening skin irritants was evaluated. The test chemicals were selected from ECETOC database (1995) and the observed in vitro irritation potential was compared to ECETOC in vivo primary irritation index (PII), to EU risk phrases, and to the harmonized OECD criteria. Chemicals were applied onto the stratum corneum surface of ROC for 30 min and samples were taken from the underlying medium at 4 and 8 h after exposure. Cell membrane integrity (determined by LDH assay) and pro-inflammatory effect (determined by IL-1alpha release) were verified at both time points and correlated to PII values. The best correlation (R(2) = 0.831) was seen with LDH leakage test. Based on obtained data, chemicals were classified according to criteria defined by EU and OECD. From 12 chemicals, only two were incorrectly classified according to OECD criteria when using LDH leakage and IL-1alpha release as irritation markers. At the end of experiment, chemical-treated ROC cultures were fixed and histological changes were assessed. Typical signs for irritation were lightly stained cytoplasm, condensed nuclei, cellular vacuolization, eosinophilic cytoplasms, and blebbing. These irritation effects of chemicals were graded visually into four classes (A-D). The extent of morphological perturbations of the cultures mostly correlated with PII. The present results indicate the validity of the ROC model in predicting skin irritation potential of chemicals and show that the use of set of irritation markers with different mechanistic responses gives more information on irritation than if only one marker was used.

FK506 (Tacrolimus) Inhibition of Intracellular Production and Enhancement of Interleukin 1α through Glucocorticoid Application to Chemically Treated Human Keratinocytes

PURPOSE

Production of the proinflammatory cytokine interleukin (IL) 1alpha, which is stored in keratinocytes (KCs) and is multifunctional, may be enhanced by glucocorticoids. A study was made to confirm whether immunosuppressants such as the macrocyclic lactone FK506 (tacrolimus) possibly serve to modulate glucocorticoid- stimulated IL-1alpha production from chemically treated KCs.

METHODS

Using cultured human KCs, the effects of FK506 on the production of IL-1alpha treated with chemicals (trinitrobenzene sulfonic acid sodium salt, TNBS) plus hydrocortisone were analyzed by ELISA and mRNA expression of IL-1alpha using RT-PCR.

RESULTS

Intracellular IL-1alpha in TNBS-treated human KCs was increased with a low concentration of 10(-10)M of hydrocortisone. Further FK506 application inhibited significantly this increased production. The mRNA expression of IL-1alpha at various concentrations of chemicals was not remarkably different.

CONCLUSIONS

FK506may control the increase in IL-1alpha with glucocorticoid in KCs, suggesting FK506 to suppress harmful effects of glucocorticoids such as steroid rosacea.

Site-matched papillary and reticular human dermal fibroblasts differ in their release of specific growth factors/cytokines and in their interaction with keratinocytes

The interfollicular dermis of adult human skin is partitioned into histologically and physiologically distinct papillary and reticular zones. Each of these zones contains a unique population of fibroblasts that differ in respect to their proliferation kinetics, rates at which they contract type I collagen gels, and in their relative production of decorin and versican. Here, site-matched papillary and reticular dermal fibroblasts couples were compared to determine whether each population interacted with keratinocytes in an equivalent or different manner. Papillary and reticular fibroblasts grown in monolayer culture differed significantly from each other in their release of keratinocyte growth factor (KGF) and granulocyte-macrophage colony stimulating factor (GM-CSF) into culture medium. Some matched fibroblast couples also differed in their constitutive release of interleukin-6 (IL-6). Papillary fibroblasts produced a higher ratio of GM-CSF to KGF than did corresponding reticular fibroblasts. Interactions between site-matched papillary and reticular couples were also assayed in a three-dimensional culture system where fibroblasts and keratinocytes were randomly mixed, incorporated into type I collagen gels, and allowed to sort. Keratinocytes formed distinctive cellular masses in which the keratinocytes were organized such that the exterior most layer of cells exhibited characteristics of basal keratinocytes and the interior most cells exhibited characteristics of terminally differentiated keratinocytes. In the presence of papillary dermal fibroblasts, keratinocyte masses were highly symmetrical and cells expressed all levels of differentiation markers. In contrast, keratinocyte masses that formed in the presence of reticular fibroblasts tended to have irregular shapes, and terminal differentiation was suppressed. Furthermore, basement membrane formation was retarded in the presence of reticular cells. These studies indicate that site-matched papillary and reticular dermal fibroblasts qualitatively differ in their support of epidermal cells, with papillary cells interacting more effectively than corresponding reticular cells.

In vitro analyses of tissue structure and interleukin-1β expression and production by human oral mucosa in response to Candida albicans infections

Clinical and experimental observations suggest that oral epithelial cells play a key role in host defenses against candidal infections through cytokines and chemokines. We thus attempted to determine whether oral epithelial cells convey IL-1beta as a pro-inflammatory cytokine in response to Candida albicans infections. We created engineered human oral mucosa (EHOM), put them in contact with live and heat-inactivated C. albicans (10(5) yeast/cm2), and measured the expression of IL-1beta mRNA and protein. Tissue structure and C. albicans morphology were also evaluated. Only live C. albicans modulated IL-1beta expression and secretion. IL-1beta mRNA expression significantly increased during the early stages of infection and decreased during the later stages. The modulatory effect of C. albicans on IL-1beta expression was confirmed by the fact that increased amounts of inactive IL-1beta (33 kDa) were detected early during the infection which then dropped dramatically. There was a significant and time-dependent increase in the amount of the active form of IL-1beta (17 kDa) secreted into the supernatant by epithelial cells infected with live C. albicans. Histological features revealed damage to infected tissues (separation of epithelial cells, edema, vacuolization, reduction in thickness) compared to uninfected ones. Morphological analyses showed that C. albicans changed from a blastospore to a hyphal form at later infection periods. This transformation was very pronounced at 8 and 24 h post-infection. These results provide additional evidence for the contribution of oral epithelial cells to local defenses against exogenous stimulations such as C. albicans infections.

Analysis of interleukin-1alpha (IL-1alpha) and interleukin-8 (IL-8) expression and release in in vitro reconstructed human epidermis for the prediction of in vivo skin irritation and/or sensitization

In the present study, reconstructed human epidermis (RHE) was used as an in vitro model to discriminate 1-chloro-2,4-dinitrobenzene (DNCB), nickel sulfate (NiSO(4)), oxazolone (OXA), 2,4-dinitrofluorobenzene (DNFB) and 2,4,6-trinitrobenzenesulfonic acid (TNBS) as skin sensitizers from benzalkonium chloride (BC), benzoic acid (BA) and sodium lauryl sulfate (SLS) as skin irritants. Our criteria were (a) the differential IL-1alpha and IL-8 synthesis and release (b) cytotoxicity assessment by MTT assay. When the RHE are topically treated with the sensitizers, very low levels of extra- and intracellular IL-1alpha are observed although they induce significant cytotoxicity. In contrast, they exhibit a sharp maximum of IL-8 release. In the presence of the tested irritants, we observe the inverse cytokine release profile, although they induce dose-dependent cytotoxicity profiles similar to those observed with the sensitizers. Finally, IL-1alpha mRNA upregulation is observed after topical application of both sensitizers and irritants, but only the latter significantly increase extracellular IL-1alpha. In conclusion, our results suggest that the associated determination of IL-8, with IL-1alpha, and MTT conversion are at least necessary to discriminate and classify, in a single assay, irritant and sensitizing agents and represent a potential in vitro alternative to two classical in vivo assays.

Keratinocytes and cytokines

The skin has long been recognized as a major producer of cytokines, but the keratinocyte as principal epidermal cell has received less attention as potential source and target of cytokines. Nevertheless, keratinocytes produce a plethora of cytokines including interleukin (IL)-1, -6, -7, -8, -10, -12, -15, -18, and -20, and tumor necrosis factor alpha (TNF). The production by keratinocytes of pro-inflammatory (IL)-1, -6, -8, and TNF was recognized early and is well studied. Keratinocyte-derived IL-7 and -15 are considered to be significant in T-cell trafficking, possibly even in the pathogenesis of cutaneous T-cell lymphoma. Immunomodulatory IL-10 and -12 originating from keratinocytes are considered to be responsible for systemic effects, and IL-18 perhaps has a similar action. Keratinocytes were fairly recently recognized as being source or target of other IL-10 family members like IL-20 and IL-24 and the role of these cytokines in specific diseases is under investigation. In addition, a variety of cytokine receptors are present on keratinocytes like those for IL-4, -13, and -17 and to lesser degree IL-2. The ability to study the expression of cytokines by keratinocytes in vivo and in vitro using primary cells, immortalized cells or even organotypic culture systems offers many possibilities to further investigate the role of cytokine production in keratinocyte biology and disease.

Ultraviolet light induced injury: immunological and inflammatory effects

This article reviews many of the complex events that occur after cutaneous ultraviolet (UV) exposure. The inflammatory changes of acute exposure of the skin include erythema (sunburn), the production of inflammatory mediators, alteration of vascular responses and an inflammatory cell infiltrate. Damage to proteins and DNA accumulates within skin cells and characteristic morphological changes occur in keratinocytes and other skin cells. When a cell becomes damaged irreparably by UV exposure, cell death follows via apoptotic mechanisms. Alterations in cutaneous and systemic immunity occur as a result of the UV-induced inflammation and damage, including changes in the production of cytokines by keratinocytes and other skin-associated cells, alteration of adhesion molecule expression and the loss of APC function within the skin. These changes lead to the generation of suppressor T cells, the induction of antigen-specific immunosuppression and a lowering of cell-mediated immunity. These events impair the immune system's capacity to reject highly antigenic skin cancers. This review gives an overview of the acute inflammatory and immunological events associated with cutaneous UV exposure, which are important to consider before dealing with the complex interactions that occur with chronic UV exposure, leading to photocarcinogenesis.

Impaired skin wound healing in peroxisome proliferator-activated receptor (PPAR)alpha and PPARbeta mutant mice

We show here that the alpha, beta, and gamma isotypes of peroxisome proliferator-activated receptor (PPAR) are expressed in the mouse epidermis during fetal development and that they disappear progressively from the interfollicular epithelium after birth. Interestingly, PPARalpha and beta expression is reactivated in the adult epidermis after various stimuli, resulting in keratinocyte proliferation and differentiation such as tetradecanoylphorbol acetate topical application, hair plucking, or skin wound healing. Using PPARalpha, beta, and gamma mutant mice, we demonstrate that PPARalpha and beta are important for the rapid epithelialization of a skin wound and that each of them plays a specific role in this process. PPARalpha is mainly involved in the early inflammation phase of the healing, whereas PPARbeta is implicated in the control of keratinocyte proliferation. In addition and very interestingly, PPARbeta mutant primary keratinocytes show impaired adhesion and migration properties. Thus, the findings presented here reveal unpredicted roles for PPARalpha and beta in adult mouse epidermal repair.

A role for mitogen-activated protein kinase activation by integrins in the pathogenesis of psoriasis

In normal epidermis, beta1 integrin expression is confined to the basal layer, whereas in hyperproliferative epidermis, integrins are also expressed in the suprabasal layers. Transgenic mice in which integrins are expressed suprabasally via the involucrin promoter have a sporadic psoriatic phenotype; however, the mechanism by which integrins contribute to the pathogenesis of psoriasis is unknown. We observed activation of mitogen-activated protein kinase (MAPK) in basal and suprabasal keratinocytes of human and transgenic mouse psoriatic lesions and healing mouse skin wounds, correlating in each case with suprabasal integrin expression. Phenotypically normal human and transgenic mouse epidermis did not contain activated MAPK. Transgene-positive keratinocytes produced more IL-1alpha than controls did, and keratinocyte MAPK could be activated by ligation of suprabasal integrins or treatment with IL-1alpha. Constitutive activation of MAPK increased the growth rate of human keratinocytes and delayed the onset of terminal differentiation, recreating many of the histological features of psoriatic epidermis. We propose that activation of MAPK by integrins, either directly or through increased IL-1alpha production, is responsible for epidermal hyperproliferation in psoriasis and wound healing, and that the sporadic phenotype of the transgenic mice may reflect the complex mechanisms by which IL-1 release and responsiveness are controlled in skin.

Immune responses in tuberculosis: antibodies and CD4-CD8 lymphocytes with vascular adhesion molecules and cytokines (chemokines) cause a rapid antigen-specific cell infiltration at sites of bacillus Calmette-Guérin reinfection

Rabbit primary dermal bacillus Calmette-Guérin (BCG) lesions were compared with reinfection BCG lesions in order to gain insight into how immune responses protect against clinical tuberculosis. As early as 3 hr, a marked infiltration of macrophages and lymphocytes occurred in the reinfection group, while very little cell infiltration occurred in the primary group. It seems that only an antigen-antibody reaction could produce such an immediate pronounced antigen-specific chemotactic effect, because very few lymphocytes are normally present in the skin. Therefore, antibodies hasten the accumulation of an expanded antigen-specific T-lymphocyte population (memory cells) at sites of bacillary lodgement. By 1-2 days, the primary and reinfection BCG lesions differed 400- to 500-fold in size. By 4-5 days, the size of the reinfection lesions had declined, while the size of the primary lesions had increased, so that, grossly, both types of lesion were similar. At 8 days in reinfection lesions and at 12 days in primary lesions, small secondary peaks in size occurred, which were probably caused by cell-mediated immune responses. In rabbits with primary BCG lesions, skin tests with Old Tuberculin were positive at 9 days, accompanied by a rise in the levels of antibodies to the secreted antigen, phosphate-specific transport protein 1, but the levels of antibodies to the constitutive antigens, purified protein derivative and heat-shock protein 65, did not increase appreciably until some time after 23 days. In tissue sections of reinfection BCG lesions, the percentage of mononuclear cells labelled, by in situ hybridization techniques, for the mRNA of monocyte chemoattractant protein 1 (MCP-1), a chemokine, peaked at 3 hr and then was down-regulated, whereas in primary lesions, this percentage was down-regulated only after 2 days. [The percentage in the tissue sections for the mRNAs of interleukins 1beta and 8, as well as the proteins of MCP-1 and tumor necrosis factor alpha (TNF-alpha), followed a somewhat similar time-course to that of MCP-1 mRNA.] A high percentage of mononuclear cells containing the MCP-1 mRNA 'factory' would favour enlargement of the lesions and a low percentage would favour their regression. At 5 days, the percentage of CD4 and CD8 lymphocytes, stained by immunohistochemical techniques, and the amount of microvasculature stained similarly for vascular cell adhesion molecule 1 were higher in the reinfection group, indicating that prior immunization caused a more rapid (antigen-dependent) up-regulation of these factors. Tuberculin reactions resembled early reinfection BCG lesions in almost every factor evaluated herein. In brief, the production of chemokines began soon after BCG reinfection, peaked within a few hours and was markedly down-regulated by 24 hr, a time at which the lesions of reinfection were of maximal size. Therefore, the amount of cell infiltration was tightly controlled, probably by the variety of mechanisms listed herein.

Functional caspase-1 is required for Langerhans cell migration and optimal contact sensitization in mice

Langerhans cell (LC) migration from epidermis to draining lymph node is a critical first step in cutaneous immune responses. Both TNF-alpha and IL-1 beta are important signals governing this process, but the potential regulatory role of IL-1 alpha processing by caspase-1 is unknown. In wild-type (WT) mice, application of the contact allergens 2,4-dinitrofluorobenzine and oxazolone lead to a marked reduction in epidermal LC numbers, but in caspase-1-deficient mice this reduction was not observed. Moreover, although intradermal injection of TNF-alpha (50 ng) induced epidermal LC migration in WT mice, this cytokine failed to induce LC migration in caspase-1-deficient mice. Intradermal IL-1 beta (50 ng) caused a similar reduction in epidermal LC numbers in both WT and caspase-1-deficient mice, indicating that, given an appropriate signal, caspase-1-deficient epidermal LC are capable of migration. Contact hypersensitivity to both 2,4-dinitrofluorobenzine and oxazolone was inhibited in caspase-1-deficient mice, indicating a functional consequence of the LC migration defect. In organ culture the caspase-1 inhibitor Ac-YVAD-cmk, but not control peptide, potently inhibited the epidermal LC migration that occurs in this system, and reduced spontaneous migration of LC was observed in skin derived from caspase-1-deficient mice. Moreover, Ac-YVAD-cmk applied to BALB/c mouse skin before application of contact sensitizers inhibited LC migration and contact hypersensitivity in vivo. Taken together, these data indicate that caspase-1 may play a central role in the regulation of LC migration and suggest that the activity of this enzyme is amenable to control by specific inhibitors both in vivo and in vitro.

Solar ultraviolet-induced erythema in human skin and nuclear factor-kappa-B-dependent gene expression in keratinocytes are modulated by a French maritime pine bark extract

The procyanidin-rich French maritime pine bark extract Pycnogenol (PBE) has been investigated for its effect in protecting human skin against solar UV-simulated light-induced erythema. Twenty-one volunteers were given an oral supplementation of Pycnogenol: 1.10 mg/kg body weight (b. wt.)/d for the first 4 weeks and 1.66 mg/kg b. wt./d for the next 4 weeks. The minimal erythema dose (MED) was measured twice before supplementation (baseline MED), once after the first 4 weeks of supplementation, and a last time at the end of the study. The UVR dose necessary to achieve 1 MED was significantly increased during PBE supplementation. Since the activation of the pro-inflammatory and redox-regulated transcription factor NF-kappaB is thought to play a major role in UVR-induced erythema, the effect of PBE was also investigated in the human keratinocyte cell line HaCaT. PBE, added to the cell culture medium, inhibited UVR-induced NF-kappaB-dependent gene expression in a concentration-dependent manner. However, NF-kappaB-DNA-binding activity was not prevented, suggesting that PBE affects the transactivation capacity of NF-kappaB. These data indicate that oral supplementation of PBE reduces erythema in the skin. Inhibition of NF-kappaB-dependent gene expression by PBE possibly contributes to the observed increase in MED.

Selective induction of cell-associated interleukin-1alpha in murine keratinocytes by chemical allergens

Cytokines may be useful tools to discriminate between irritant and allergic contact dermatitis. In the mouse only, it has been demonstrated by other, that contact sensitizers up-regulated keratinocytes-derived interleukin-1alpha (IL-1), macrophage inflammatory protein-2 and interferon induced protein 10 mRNAs. The purpose of this study was to investigate the possibility to use in vitro IL-1 production by a murine keratinocyte cell line for preliminary screening of chemicals for their irritant and/or allergic potential. We investigated the effects of five relevant skin allergens (dinitrochlorobenzene, oxazolone, nickel sulfate, penicillin G and eugenol), two skin irritants (benzalkonium chloride, and methylsalicilate) and two compounds with no sensitizing activity (glycerol and ethanol) on IL-1 production in HEL30 cells. Twenty four hours following treatment, both IL-1 release in conditioned media and cell-associated IL-1 were measured by a specific sandwich ELISA. Under our experimental conditions, only contact sensitizers were able to increase in a dose dependent fashion cell-associated IL-1, confirming the in vivo findings. Both skin irritants and allergens induced the release of IL-1, because of the irritative properties of both chemicals, while ethanol and glycerol failed to induce changes in IL-1 production, confirming the specificity of the proposed test. Taken together, these data indicate that it may be realistic to consider potential skin allergens those chemicals which are able to increase cell-associated IL-1, to consider skin irritants those chemicals which induce only IL-1 release, and to exclude as potential allergens or irritants those chemicals which fail to induce changes in IL-1 production.

Topical FK506 Suppresses Cytokine and Costimulatory Molecule Expression in Epidermal and Local Draining Lymph Node Cells During Primary Skin Immune Responses

Recently, it has been shown that the immunosuppressive macrolide lactone, FK506, exerts good therapeutic efficacy in inflammatory skin diseases. The aim of this study was to analyze the influence of topical FK506 on molecular (IL-1α, IL-1β, IL-2, IL-4, IL-12 p35, IL-12 p40, macrophage inflammatory protein-2 (MIP-2), granulocyte-macrophage CSF (GM-CSF), TNF-α, and IFN-γ) and cellular (I-A+/CD80+, I-A+/CD54+, I-A+/CD69+, I-A+/B220+, and CD4+/CD25+) events in epidermal (EC) and local draining lymph node (LNC) cells during primary contact hypersensitivity responses. Cytokine mRNA levels for IL-1α, IL-1β, GM-CSF, TNF-α, MIP-2, and IFN-γ in EC and for IL-2, IL-4, IL-12 p35, IL-12 p40, and IFN-γ in LNC were increased and resulted in significant LNC proliferation during oxazolone-induced contact hypersensitivity. Topical FK506 treatment dose-dependently suppressed oxazolone-induced LNC proliferation. This effect was correlated with decreased IL-1α, IL-1β, GM-CSF, TNF-α, MIP-2, and IFN-γ mRNA expression within the epidermis and decreased IL-12 p35 and p40 mRNA expression in LNC. Further analysis of the LNC cytokine pattern revealed that the production of both Th1 (IFN-γ and IL-2) and Th2 (IL-4) cytokines was dramatically impaired after topical FK506 treatment. Flow cytometric analysis showed that topical FK506 decreased the population of epidermis-infiltrating CD4+ T cells and suppressed the expression of CD54 and CD80 on I-A+ EC and LNC during hapten-induced contact hypersensitivity. Furthermore, topical FK506 profoundly impaired oxazolone-induced up-regulation of CD25 expression on CD4+ LNC and dramatically decreased hapten-induced expansion of I-A+/B220+ and I-A+/CD69+ LNC subsets. In conclusion, these results give new insights into the mechanisms of action of topical FK506 treatment.

Proteolytic activation of the interleukin-1beta precursor by Candida albicans

Chronic inflammation rather than invasion is characteristic of some forms of superficial candidiasis such as denture stomatitis. We hypothesized that Candida albicans may play a critical role in the pathogenesis of inflammatory lesions observed in chronic candidiasis by activating the proinflammatory cytokine interleukin-1beta (IL-1beta) from epithelial stores of the precursor. The aim of this study was therefore to demonstrate the proteolytic cleavage and activation of the inactive precursor of IL-1beta (pro-IL-1beta) by C. albicans. After incubation of either blastospores or hyphae with the inactive precursor, proteolytic cleavage was monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis Western immunoblotting analysis, and the biological activity of the cleavage products was tested in a bioassay. We report here that late-stationary-growth-phase blastospores as well as hyphae of C. albicans, but not exponentially growing cells, can efficiently cleave pro-IL-1beta to yield fragments of molecular masses compatible with mature biologically active IL-1beta (17 to 19 kDa). Assays conducted in the presence of selected proteinase inhibitors suggest that the cleavage of pro-IL-1beta involves the participation of one or more aspartyl proteinases. Cleavage products showed a dose-dependent IL-1beta-like activity in a thymocyte proliferation bioassay, which was inhibited by anti-IL-1beta neutralizing antibodies. The present data thus suggest a role for C. albicans proteinases in the activation and maintenance of the inflammatory response at epithelial surfaces.

Prednicarbate versus conventional topical glucocorticoids: pharmacodynamic characterization in vitro

PURPOSE

Pharmacodynamic characterization of topical glucocorticoids as prednicarbate (PC), its metabolites prednisolone 17-ethylcarbonate (PEC) and prednisolone (PD), betamethasone 17-valerate (BMV), betamethasone (BM) and desoximetasone (DM) by evaluating their effects on epidermal and dermal cells. Synopsis of pharmacokinetic and pharmacodynamic studies, possibly explaining the improved benefit-risk ratio of prednicarbate.

METHODS

Isolated foreskin keratinocytes were used to investigate the influence on epidermal inflammatory processes, dermal fibroblasts of the same origin to study antiproliferative activities of glucocorticoids. Interleukins were measured by ELISA-assay, the influence on II-1 alpha-production also on mRNA-level by RNAse protection assay. Proliferation was assessed by 3H thymidine incorporation and biodegradation by HPLC/UV-absorption. Cell viability was controlled by MTT assay.

RESULTS

In keratinocytes, inflammation was induced by TNF alpha, resulting in an increased II-1 alpha synthesis. This cytokine was particularly suppressed by PC and BMV, whereas PEC, PD, DM and BM were less potent (p < or = 0.05). Since, however, the double ester PC is rapidly degraded in keratinocytes, a RNAse-protection assay of II-1 alpha mRNA was performed allowing short incubation times and thus minimizing biodegradation effects. In agreement with the previous experiment, the antiinflammatory potency of native PC was confirmed. In fibroblasts, II-1 alpha and II-6 synthesis indicate proliferation and inflammation respectively. Whereas PC inhibited II-1 alpha and II-6 production in fibroblasts to a minor extent only, it was strongly reduced by the conventional glucocorticoids and PEC (p < or = 0.05). The minor unwanted effect of PC on fibroblasts was also reflected by its low influence on cell proliferation as assayed by 3H thymidine incorporation. More pronounced antiproliferative features were observed with BM, PEC and especially BMV.

CONCLUSIONS

Correlating antiphlogistic effects in keratinocytes (suppression of II-1 alpha) with antiproliferative effects in fibroblasts (suppression of II-1 alpha and II-6), the improved benefit-risk ratio of PC compared to conventional glucocorticoids does not result only from distinct drug metabolism in the skin but also from a specific influence on the cytokine network.

Keratinocyte expression of the type 2 interleukin 1 receptor mediates local and specific inhibition of interleukin 1-mediated inflammation

Epidermal keratinocytes can express two types of interleukin 1 (IL-1) receptors: IL-1R1, which is active in signal transduction, and the less well characterized IL-1R2, which is incapable of transducing a signal and can be shed from cells. The binding of IL-1 in solution by IL-1R2 has been demonstrated, and it has been proposed to inhibit IL-1-mediated responses through this mechanism. We and others have reported that keratinocytes can be induced to express IL-1R2 both in vitro and in vivo, often under conditions that also favor IL-1 gene expression. We hypothesized that production of IL-1R2 by keratinocytes would be an efficient means to achieve local inhibition of IL-1-mediated responses without systemic consequences. To test this hypothesis, we have generated transgenic mice that constitutively express IL-1R2 on basal keratinocytes. Keratinocytes cultured from these animals shed the soluble form of the receptor into culture supernatants, and IL-1-inducible production of granulocyte/macrophage colony-stimulating factor was markedly inhibited. In vivo, acute cutaneous vascular leakage, as well as chronic inflammation induced by a well characterized IL-1-dependent stimulus, was significantly inhibited in IL-1R2 transgenic animals. In contrast, contact hypersensitivity was unaffected, suggesting that overexpression of IL-1R2 did not inhibit all types of inflammation globally. Finally, systemic injection of IL-1 induced equivalent levels of plasma IL-6 in IL-1R2 transgenic and nontransgenic mice, suggesting that the activity of the transgenic IL-1R2 remained predominantly local and did not influence systemic IL-1 responses. We conclude that tissue-specific production of IL-1R2 can mediate IL-1 antagonism in tissue microenvironments without systemic consequences. Our transgenic mice may be a useful tool for determining the degree to which different types of cutaneous inflammation depend on the IL-1 system.

Differences in responses of interleukin-1 and tumor necrosis factor alpha production and secretion to cyclosporin-A and ultraviolet B-irradiation by normal and transformed keratinocyte cultures

Among epidermal cytokines, IL-1 and TNF alpha are involved in inflammatory skin reactions and suspected of modulation by immunosuppressive treatment (e.g., cyclosporin A, CsA) or UVB-irradiation, 2 mediators probably being involved in epithelial carcinogenesis. We evaluated the effects of 8 micrograms/ml CsA and 100 J/m2 UVB-irradiation on the production and secretion of IL-1 and TNF alpha on normal human epidermal keratinocytes (NHK) and epidermal keratinocyte cell lines either spontaneously transformed (HaCaT) or transformed by human papillomavirus (HPV) type 16 or 18 (EK 16 and EK18), by using ELISA test. Normal and immortalized keratinocytes constitutively produced and released IL-1 alpha, IL-1 beta and IL-1 receptor antagonist (IL-1RA) but IL-1 synthesis by NHK was significantly higher than by cell lines. All the cells spontaneously excreted low amounts of TNF alpha. Different responses to treatments were evidenced between NHK and cell lines. CsA modified significantly the production and secretion of IL1 in most cells whereas slight changes were observed with TNF alpha secretion. UVB irradiation had no effect on the intracellular IL1 pool of any cells but increased the release of IL1 and TNF alpha. The association CsA-UVB did not result in additive effects on synthesis and secretion of IL1; the release of TNF alpha by the cells remained poor except for EK18 cells. Taken together, these results show that, in immortalized keratinocytes, the IL-1 and TNF alpha expression was differently affected by treatments with CsA and/or UVB-irradiation as compared to NHK. In addition, spontaneously transformed keratinocytes, HaCaT, reacted differently from HPV-transformed keratinocytes, EK16 and EK18.

Inflammatory and hyperproliferative skin disease in mice that express elevated levels of the IL-1 receptor (type I) on epidermal keratinocytes. Evidence that IL-1-inducible secondary cytokines produced by keratinocytes in vivo can cause skin disease

Interleukin (IL)-1 induces a cascade of secondary cytokines in a large number of cell types in vitro, including monocytes, fibroblasts, synovial cells, and keratinocytes. Although it has been proposed that autocrine or paracrine activation of such cells by IL- 1 in situ could orchestrate a local inflammatory response, formal proof for such an hypothesis has been lacking. In an attempt to lower the threshold for secondary cytokine production in these cells in response to IL-1, we have generated transgenic mice (designated IR10) which overexpress functional type 1 IL-1 receptor in basal layer of epidermis keratinocytes. As predicted, keratinocytes from these animals were substantially more responsive to exogenous IL-1 than nontransgenic keratinocytes when stimulated in vitro. When challenged with known inducers of keratinocyte IL-1 synthesis and release, skin of IR10 mice exhibited an exaggerated inflammatory response, characterized by epidermal hyperplasia and an acute dermal inflammatory cell infiltrate. In this setting, the secondary epidermal cytokines gro-alpha and GM-CSF were strongly induced in transgenic epidermis but not in control skin. To confirm that these changes were indeed related to IL-1 mediated activation pathways, IR10 mice were crossed to a distinct line of transgenic mice that overexpress 17-kD IL-l alpha in basal keratinocytes. Double transgenic mice derived from this cross breeding experiment developed spontaneous inflammation of the skin, similar in appearance to that induced by PMA, both histologically and macroscopically, and distinct from that seen in either parental strain spontaneously. Furthermore, secondary cytokines were more strongly induced in the double transgenic than in either parental strain. These findings conclusively demonstrate the potential for functional autocrine pathways of keratinocyte activation mediated by IL-1 alpha in vivo, and suggest that level of expression of type 1 IL-1 receptor may function as a significant control point in physiologic IL-1 mediated autocrine pathways.