Identification of immature cornified envelopes in the barrier-impaired epidermis by characterization of their hydrophobicity and antigenicities of the components

Cornified envelopes (CEs), rigid and insoluble structures in the stratum corneum, which are assembled by crosslinking of several precursor proteins by transglutaminases, provide a hydrophobic foundation for barrier function; omega-hydroxyceramides are covalently attached to the outer surface of CE components, and onto this hydrophobic assembly, lamellar layers of intercellular lipids are organized. Morphologically irregular, fragile CEs are found in the deep layer of the stratum corneum or in certain disorders, such as psoriasis, whereas most CEs from healthy subjects are rigid and polygonal. We have established a staining method to characterize such fragile CEs as immature and less hydrophobic CEs, and employed it to examine regional differences in the properties of CEs, especially in relation to the barrier function of the skin. CEs from the outermost stratum corneum of the trunk and extremities of healthy subjects were relatively uniform in morphology with larger shape, and were homogeneous in hydrophobicity as judged from the use of an environment-sensitive fluorescent dye, Nile red. However, CEs from the face were strikingly heterogeneous, and consisted of both rigid and fragile CEs. Rigid CEs were Nile red-positive and little stained by anti-involucrin. In contrast, fragile CEs were Nile red-negative but strongly stained with anti-involucrin, as detected by indirect immunofluorescence. Thus, CEs from the face were stained with Nile red or involucrin in a mutually exclusive manner. Fragile CEs were stained with antibodies against other CE components, including loricrin, envoplakin, filaggrin, and isopeptides. Such fragile, involucrin-positive CEs were detected not only in the face, but also in the deep layer of the stratum corneum of the arm. In addition, experimental barrier disruption resulted in the appearance of involucrin-positive CEs in the outermost stratum corneum. These results suggest that involucrin-positive, fragile CEs are immature and less hydrophobic, and that their occurrence is closely related to impairment of the barrier function of the skin.     

Stratum corneum lipid profile and maturation pattern of corneocytes in the outermost layer of fresh scars: the presence of immature corneocytes plays a much more important role in the barrier dysfunction than do changes in intercellular lipids

BACKGROUND: The functional characteristics of the stratum corneum (SC) of fresh scars as well as keloids and hypertrophic scars are characterized by elevated transepidermal water loss (TEWL) and increased SC hydration. OBJECTIVES: To study the composition of the intercellular lipids and maturation properties of the cornified envelope (CE) of the SC, as these are the most important components for the SC barrier function in fresh scars. METHODS: SC lipids were extracted from the donor site for split-thickness skin grafting soon after re-epithelialization using a cup method, and were analysed with high-performance thin-layer chromatography. CEs, which were prepared from superficial layers of the SC, were double stained with Nile red and anti-involucrin. RESULTS: We found a significant decrease in the proportion of ceramide (CER) in the SC lipids of fresh scars. We also observed changes in the SC CER profile that consisted of an increase in CER 4 and CER 7 and a decrease in CER 3, without any significant change in the proportion of CER 1. These changes were insufficient to explain the remarkably high TEWL recorded in the early stage of fresh scars. In contrast, with double staining of CE with Nile red and anti-involucrin, we detected the presence of numerous immature and less hydrophobic corneocytes in the outermost layer of the SC of fresh scars. Scanning electron microscopy of such corneocytes revealed numerous fine wrinkles on their enlarged surface area. Most of all, we found a closely similar, time-dependent, exponential decrease in the ratio of immature corneocytes with a poorly hydrophobic CE and in the recorded TEWL values in fresh scars. There was a highly significant positive correlation between the proportion of immature corneocytes in the outermost layer of the SC and TEWL values. CONCLUSIONS: These results suggest that the SC barrier dysfunction of the fresh scars is attributable to the presence of immature corneocytes with a less hydrophobic CE, rather than to the changes in SC lipid composition.     

Basis for the permeability barrier abnormality in lamellar ichthyosis

The basis for the permeability barrier abnormality in lamellar ichthyosis (LI) is not known. LI is caused by mutations in the gene that encodes the enzyme, transglutaminase 1 (TGI), which is responsible for assembly of the cornified envelope (CE). TG1 also has been suggested recently to catalyze the covalent attachment of omega-hydroxyceramides (omega-OHCer) to the CE, forming the corneocyte-lipid envelope (CLE). We first assessed the barrier function and the permeability pathway of the water-soluble tracer, colloidal lanthanum, across the stratum corneum (SC) in patients with LI with absent (n = 4) or low (n = 2) TG1 activity/protein. Increased movement of tracer through the SC correlated with increased transcutaneous water loss, and tracer remained restricted to the SC interstices. Enhanced extracellular permeability, in turn, was explicable by truncation and fragmentation of extracellular lamellar membrane arrays. The resultant clefts in the SC interstices represent the likely pathway for increased water permeability. Moreover, tracer movement remained restricted to the interstices, despite the demonstration of increased corneocyte fragility associated with widespread variations in CE structure. Regardless of variability in CE structure, however, CLE structure and bound omega-OHCer content were normal. The normal CLE in LI may explain both the restriction of tracer to the SC interstices, as well as the presence of foreshortened membrane arrays with near-normal interlamellar dimensions. Finally, the demonstration of a normal CLE in LI also raises questions about the putative role of TG1 in forming the CLE. These results demonstrate: (1) the extracellular nature of increased permeability in LI; (2) discontinuities in extracellular membrane structures that account for the enhanced permeability in LI; (3) that these membrane abnormalities are both associated with and explained by abnormalities in the subjacent CE scaffold; and (4) an intact CLE is present in LI, despite abnormalities in the CE, which may restrict water movement to the SC interstices in LI.     

Differential expression of cornified cell envelope precursors in normal skin,intraorally transplanted skin and normal oral mucosa

BACKGROUND: Skin flaps have routinely been used as substitutes for oral mucosa after extensive resection of oral tissues. However, it remains unknown how the transplanted skin flaps perform as a host defence in the new environment of the oral cavity. OBJECTIVES: To evaluate the expression of cornified cell envelope (CCE) precursors in pretransplanted (normal) skin, intraorally transplanted skin and normal oral mucosa, because CCEs are highly responsible for a protective barrier in each type of epithelium. METHODS: We used immunohistochemistry and immunoelectron microscopy to examine the expression of CCE precursors, small proline-rich protein (SPR) 2 and 3 and loricrin, in biopsy specimens of normal skin, transplanted skin and normal oral mucosa, including buccal and lingual (non-keratinized) mucosae, and palatal (keratinized) mucosa. RESULTS: Transplanted skin flaps were classified into two groups. About two-thirds of the transplanted skin flaps displayed a reddish appearance and were devoid of the stratum corneum (SC) together with a psoriasiform inflammatory tissue reaction. Others showed a native appearance, retaining the SC. While SPR2 expression was limited to the stratum granulosum (SG) in both normal and transplanted skin retaining the SC, it extended to the stratum spinosum (SS) of the transplanted skin lacking the SC and that of the normal oral mucosa. Although SPR3 expression was not found in normal skin or in the transplanted skin retaining the SC, it was strongly expressed in the SS of the transplanted skin lacking the SC and the non-keratinized oral mucosa, and in the SS and SG of the keratinized oral mucosa. Loricrin, which was expressed in the SG of normal skin, the transplanted skin retaining the SC and the keratinized oral mucosa, was not detected in the transplanted skin lacking the SC or in the non-keratinized oral mucosa. Immunoelectron microscopy confirmed the ultrastructural localization of SPR3 directly under the cytoplasmic membrane of keratinocytes of the transplanted skin lacking the SC and that of the oral mucosa. CONCLUSIONS: The altered expression of SPR2, SPR3 and loricrin reflects the possible adaptation of epidermal keratinocytes in the new environment of the oral cavity.     

Expression of differential genes involved in the maintenance of water balance in human skin by Piptadenia colubrina extract

Background  Hydration and integrity of the stratum corneum (SC) is an important determinant of skin appearance, metabolism, mechanical properties, and barrier function. The presence of aquaglyceroporins and envelope proteins are crucial to provide greater corneocyte cohesion to keep water and other moisturizers in the skin.
Aims  In this study, we evaluated the ability of Piptadenia colubrina , a plant native of South American rain forests, in the expression of genes involved in skin capacitance and SC integrity.
Methods  The expression of genes for aquaporin-3 (AQP3), loricrin, involucrin (INV), and filaggrin (FLG) was measured by real-time PCR, using an in vitro model of human keratinocytes incubated with concentrations of 2.5, 5, 10, and 20 mg/mL of a hydroglycolic extract of P. colubrina (HEPC). The amount of AQP3 protein was also tested by immunohistochemistry in human skin explants. Clinical trials were conducted to evaluate the effects of a gel-cream containing HEPC on the glycerol index and skin capacitance.
Results  Hydroglycolic extract of P. colubrina increased both the expression and immunoreactivity of AQP3 in cultured keratinocytes and human skin explants. The gene induction to envelope proteins FLG and INV was also observed after cell incubation with HEPC. Skin capacitance was significantly improved in human volunteers under treatment with HEPC-containing cream.
Conclusions  The extract of P. colubrina promotes cellular hydration and induces gene expression of envelope proteins providing greater corneocyte cohesion to keep water and other moisturizers in the skin and an appropriate epidermal adhesion. The in vitro findings were clinically confirmed and encourage the clinical use of this compound in skin care products.     

Structural organization of cornified cell envelopes and alterations in inherited skin disorders

Abstract: The cornified cell envelope is a highly insoluble and extremely tough structure formed beneath the cell membrane during terminal differentiation of kerationcytes. Its main function is to provide human skin with a protective barrier against the environment. Sequential cross-linking of several integral components catalyzed by transglutaminases leads to a gradual increase in the thickness of the envelope and underscores its rigidity. Key structural players in this cross-linking process include involucrin, loricrin, SPRRs, elafin, cystatin A, S100 family proteins, and some desmosomal proteins. The recent identification of genetic skin diseases with mutations in the genes encoding some of these proteins, including transglutaminase 1 and loricrin, has disclosed that abnormal cornified cell envelope synthesis is significantly involved in the pathophysiology of certain inherited keratodermas and reflects perturbations in the complex yet highly orderly process of cornified cell envelope formation in normal skin biology.     

Age‐related changes in the composition of the cornified envelope in human skin

The main function of the epidermis is to protect us against a multitude of hostile attacks from the environment. Its main cell type, the keratinocytes have a sophisticated system of different proteins and lipids available to form the cornified envelope, which is responsible for the barrier function of the skin. During ageing, dramatic changes are taking place. Some proteins of the SPRR‐, S100‐ and LCE3‐family are massively up‐regulated, whereas others like loricrin, filaggrin and the LCE1&2 protein families are significantly down‐regulated. The latter ones are known to be under control of calcium and/or ‘calcium response elements’. We were able to show that the calcium peak specific for the stratum granulosum, which is the site where loricrin and the LCE1&2 families are synthesized, is reduced during ageing. The resulting cornified envelope in old skin has an extensively changed composition on the molecular level compared to young skin. This knowledge is of critical importance to understand chronic wound formation and ulcers in old age.     

Molecular interactions of plant oil components with stratum corneum lipids correlate with clinical measures of skin barrier function

Plant‐derived oils consisting of triglycerides and small amounts of free fatty acids (FFAs) are commonly used in skincare regimens. FFAs are known to disrupt skin barrier function. The objective of this study was to mechanistically study the effects of FFAs, triglycerides and their mixtures on skin barrier function. The effects of oleic acid (OA), glyceryl trioleate (GT) and OA/GT mixtures on skin barrier were assessed in vivo through measurement of transepidermal water loss (TEWL) and fluorescein dye penetration before and after a single application. OA's effects on stratum corneum (SC) lipid order in vivo were measured with infrared spectroscopy through application of perdeuterated OA (OA‐d₃₄). Studies of the interaction of OA and GT with skin lipids included imaging the distribution of OA‐d₃₄ and GT ex vivo with IR microspectroscopy and thermodynamic analysis of mixtures in aqueous monolayers. The oil mixtures increased both TEWL and fluorescein penetration 24 h after a single application in an OA dose‐dependent manner, with the highest increase from treatment with pure OA. OA‐d₃₄ penetrated into skin and disordered SC lipids. Furthermore, the ex vivo IR imaging studies showed that OA‐d₃₄ permeated to the dermal/epidermal junction while GT remained in the SC. The monolayer experiments showed preferential interspecies interactions between OA and SC lipids, while the mixing between GT and SC lipids was not thermodynamically preferred. The FFA component of plant oils may disrupt skin barrier function. The affinity between plant oil components and SC lipids likely determines the extent of their penetration and clinically measurable effects on skin barrier functions.     

Large-scale DNA microarray analysis of atopic skin lesions shows overexpression of an epidermal differentiation gene cluster in the alternative pathway and lack of protective gene expression in the cornified envelope

BACKGROUND: Atopic dermatitis (AD)-specific genes have not yet been clarified. Objectives To identify gene expression specific to active atopic skin lesions. METHODS: We analysed 23,000 genes in skin biopsy samples from 17 patients with AD and four normal controls using Affymetrix oligonucleotide arrays. RESULTS: Four of the 10 genes with the greatest differences in expression between patients and controls, S100A8 and S100A7 (upregulated), and loricrin and filaggrin (downregulated), were epidermal differentiation genes located on 1q21, a locus previously reported to have a genetic linkage with AD. CONCLUSIONS: Our results, showing downregulation of the cornified envelope genes and upregulation of the alternative keratinization pathway, are the first to suggest abnormal epidermal differentiation and defective defences as key abnormalities in AD.     

Increased carbonyl protein level in the stratum corneum of inflammatory skin disorders: A non‐invasive approach

The stratum corneum (SC) is the interface of body and environment, and is continuously exposed to oxidative stress, resulting in carbonyl modification of proteins. We have developed a simple and non‐invasive method to assess carbonyl protein (CP) level in the SC, applied it to various kinds of skin, and revealed a link between the stratum corneum carbonylated protein (SCCP) level and water content in the SC. The purpose of the present study is to examine the SCCP level in inflammatory skin disorders associated with xerosis. Psoriasis vulgaris (PV) and atopic dermatitis (AD) are typical inflammatory skin disorders, of which the stratum corneum shows markedly low water content. SC samples were non‐invasively collected from the lesional and non‐lesional areas of PV and AD by adhesive tape stripping, and their carbonyl groups were determined by reaction with fluorescein‐5‐thiosemicarbazide. The average fluorescence intensity of the SC was calculated as SCCP level. Higher SCCP level was observed in the lesional area of PV as compared with non‐lesional area or healthy control. Lesional area of AD also exhibited higher SCCP level than corresponding non‐lesional area, of which SCCP level was slightly higher than the healthy control. These data suggest the involvement of oxidative modification of the SC protein, at least in part, in generation of xerotic skin in inflammatory skin disorders as well as dry skin in healthy subjects.     

Expression of small proline rich proteins in neoplastic and inflammatory skin diseases

BACKGROUND: The formation of the cornified cell envelope (CE) during the late stages of epidermal differentiation is essential for epidermal barrier function and protects the body against environmental attack and water loss. Formation of the CE involves the replacement of the plasma membrane by cross-linkage of precursor proteins such as involucrin, small proline rich proteins (SPRR) and loricrin. In normal epidermis, SPRR1 is restricted to appendages, SPRR2 is also expressed in interfollicular areas, while SPRR3 is completely absent; the latter is most abundant in oral epithelium. This differential expression indicates an important part for SPRRs in specific barrier requirements, and reflects their importance in the biomechanical properties of the CE. OBJECTIVES: We report here on the expression of SPRR1, SPRR2 and SPRR3 in a wide range of cutaneous neoplastic and inflammatory diseases. METHODS: We used immunohistochemistry; in addition, Northern blot analysis of malignant tumours was performed. RESULTS: Increased suprabasal expression of SPRR1 and SPRR2, but no SPRR3 expression, was noted in inflammatory dermatoses with orthokeratotic and parakeratotic squamous differentiation. By contrast, differentiating epidermal tumours such as Bowen's disease, keratoacanthoma and squamous cell carcinoma expressed SPRR3. CONCLUSIONS: As SPRRs were originally cloned on the basis of their expression in ultraviolet light-irradiated keratinocytes, the expression of SPRR3 in actinic lesions is of interest, and might serve as a diagnostic tool.     

Knock‐down of filaggrin does not affect lipid organization and composition in stratum corneum of reconstructed human skin equivalents

Human skin mainly functions as an effective barrier against unwanted environmental influences. The barrier function strongly relies on the outermost layer of the skin, the stratum corneum (SC), which is composed of corneocytes embedded in an extracellular lipid matrix. The importance of a proper barrier function is shown in various skin disorders such as atopic dermatitis (AD), a complex human skin disorder strongly associated with filaggrin (FLG) null mutations, but their role in barrier function is yet unclear. To study the role of FLG in SC barrier properties in terms of SC lipid organization and lipid composition, we generated an N/TERT‐based 3D‐skin equivalent (NSE) after knock‐down of FLG with shRNA. In these NSEs, we examined epidermal morphogenesis by evaluating the expression of differentiation markers keratin 10, FLG, loricrin and the proliferation marker ki67. Furthermore, the SC was extensively analysed for lipid organization, lipid composition and SC permeability. Our results demonstrate that FLG knock‐down (FLG‐KD) did not affect epidermal morphogenesis, SC lipid organization, lipid composition and SC permeability for a lipophilic compound in NSEs. Therefore, our findings indicate that FLG‐KD alone does not necessarily affect the functionality of a proper barrier function.     

Transepidermal water loss does not correlate with skin barrier function in vitro

The purpose of this study was to investigate the relationship between transepidermal water loss and skin permeability to tritiated water (3H2O) and the lipophilic penetrant sulfur mustard in vitro. No correlation was found between basal transepidermal water loss rates and the permeability of human epidermal membranes to 3H2O (p = 0.72) or sulfur mustard (p = 0.74). Similarly, there was no correlation between transepidermal water loss rates and the 3H2O permeability of full-thickness pig skin (p = 0.68). There was no correlation between transepidermal water loss rate and 3H2O permeability following up to 15 tape strips (p = 0.64) or up to four needle-stick punctures (p = 0.13). These data indicate that transepidermal water loss cannot be unconditionally ascribed to be a measure of skin barrier function. It is clear that further work should be conducted to interpret the significance of measuring transepidermal water loss by evaporimetry.     

Disruption of the suprabasal keratin network by mutation M150T in the helix initiation motif of keratin 10 does not affect cornified cell envelope formation in human epidermis

Keratin 10 (K10) is known to be tightly bound to the cornified cell envelope (CCE) and this binding is thought to play an important role in enhancing the structural integrity of the cornified cells. Bullous congenital ichthyosiform erythroderma (BCIE) is a genetic disorder of keratinization caused by gene mutations in the conserved sequences of keratin 1 (K1) or K10, which leads to abnormal suprabasal keratin network assembly. In BCIE patients' skin, the keratin network abnormalities make the upper spinous and granular keratinocytes fragile and result in blister formation. However, the exact pathomechanism of the hyperkeratosis seen in BCIE is still unknown. The involvement of the CCE in the pathomechanism of hyperkeratosis in BCIE is controversial. Abnormal CCE assembly may cause hyperkeratosis as reported in cases of lamellar ichthyosis. Binding of K10 to CCE is thought to be a vital connection between the suprabasal keratin filament network and CCE. We hypothesize that abnormal suprabasal keratin assembly caused by either K1 or K10 mutations can disrupt CCE formation, resulting in the hyperkeratosis observed in BCIE. To clarify whether K10 and keratin network defects affect CCE formation in vivo, the ultrastructural and immunohistological features of CCE were studied in the epidermis of two Japanese BCIE patients from two independent families carrying an identical missense mutation M150T in the helix initiation motif of K10. Ultrastructurally, a 15-nm-thick, dense, normal-appearing CCE was formed at the cell periphery of the keratinized epidermal cells. Light and electron microscopic immunolabeling revealed that the major CCE precursor proteins, involucrin and loricrin, were normally distributed and restricted to CCE of the epidermis. Immunofluorescent labeling showed that epidermal TGases, TGase 1, TGase 2 and TGase 3, were expressed normally in the epidermis. These findings suggest that a normal CCE is formed during the process of human epidermal keratinization, even if the suprabasal keratin filament network is disrupted as with this particular K10 mutation, M150T in BCIE.     

Development and validation of a semiautomatic image analysis system for measuring skin desquamation with D-Squames®

Background D-Squames^®, have gained wide acceptance for assessing skin desquamation. The amount of corneocytes adhering to D-Squames^® can be assessed visually by trained observers or by computerized image analysis. Different image analysis algorythms for the evaluation of D-Squames^® have been published but have not been compared with each other. It was our aim to develop an image analysis system that does not require an expensive image analysis programming tool but should be optimized for routine tasks of analysing large numbers of samples. A second objective of this study was to compare two published image analysis algorythms and visual grading. Material and Methods The hardware components of the system are a CCD camera connected to a frame grabber card and a light box equipped with fluorescent tubes on two sides that provide a relatively cool, diffuse and even illumination of the sample. The following features were included into the software: generation and identification of bar codes for sample identification; semiautomatic recognition of ROI (region of interest), integration of study design into the analysing process, rapid calculation of desquamation index (DI: integration of the per cent area covered by scales and their thickness distribution) and/or scaling index (SI: distribution of grey values), data storage and export for further analysis. In a first step the system was validated by examining D-Squames covering a wide range of desquamation, by examining different ROI shapes (circle and square), by performing repeat measurements with different positions of the samples and by repeat measurements after re-callibrating the system. In a second step the effect of treatment with different moisturizers was evaluated by the two image analysis parameters DI and SI and compared with hydration measurements (Corneometer^®). Results The shape of the ROI showed no influence on the results (variability < 5%). Reproducibility of measurements was satisfactory (COV CDI): 1.7%, COV (SI): 2.6%).There was a good correlation between image analysis results and visual evaluation (means of 3 technicians) (r = 0.986) as well as between the two different image analysis parameters DI and SI (r = 0.971). In the clinical study moisturizer treatment resulted in variable reduction of desquamation that was closely correlated with increase in stratum corneum hydration (r = 0.97). Conclusion Analysing D-Squames^® with the image analysis system proved to be reproducible, independent of the shape of ROI, cost effective and fast and easy to operate. It has shown to be a suitable and reliable method for the objective determination of desquamation levels.     

Plasminogen activator inhibitor-2 is expressed in different types of congenital ichthyosis: in vivo evidence for its cross-linking into the cornified cell envelope by transglutaminase-1

BACKGROUND: Plasminogen activator inhibitor-2 (PAI-2), a regulatory serpin of the plasminogen activator (PA) system, has been described as a potential component of the cornified cell envelope (CE). Protease inhibitors are essential for skin homeostasis and in particular for the regulation of the desquamation process. Therefore, an aberrant expression of PAI-2 could be involved in the pathogenesis of certain cornification disorders. OBJECTIVES: Evaluation of the expression of PAI-2 in different types of congenital ichthyosis, especially in lamellar ichthyosis/nonbullous congenital ichthyosiform erythroderma (LI/NCIE) and in Netherton syndrome (NTS). Demonstration of the functional relationship between PAI-2 and transglutaminase (TGase)-1. PATIENTS AND METHODS: Using immunohistochemistry we evaluated cryosections from individuals suffering from LI/NCIE (n=67), NTS (n=6), ichthyosis-follicularis-atrichia-photophobia syndrome (n=2) and Harlequin ichthyosis (n=1) in comparison with psoriasis vulgaris and healthy skin. Moreover, we assessed the respective TGase-1 activity and the presence of TGase-1 protein. A functional assay was developed to elucidate whether PAI-2 is a substrate for TGase-1. RESULTS: PAI-2 is expressed in different types of congenital ichthyosis and there is a strong correlation between TGase-1 activity and PAI-2 protein signal. Double staining revealed a strong colocalization of TGase-1 activity and PAI-2 protein. The epidermal incorporation of the specific PAI-2 peptide containing a TGase binding site revealed a strong pericellular staining in the stratum granulosum in healthy skin. In contrast, TGase-1-deficient skin showed only a lamellar staining in the stratum corneum. CONCLUSIONS: We provide in vivo evidence that PAI-2 is a substrate of TGase-1. The normal expression of PAI-2 in a large group of TGase-1-proficient LI/NCIE patients makes it rather unlikely that PAI-2 alone is a primary molecular cause of LI/NCIE.     

An increased ratio of interleukin-1 receptor antagonist to interleukin-1α in inflammatory skin diseases

Abstract: IL-1 receptor antagonist (IL-1ra) is a cytokine that competitively binds the IL-1 receptor to antagonize IL-1 activity without any agonist function. Previous experiments indicated that the ratio of IL-1ra to IL-1α in the normal stratum corneum (SC) was much higher in the sunexposed face than in the sun-protected area, upper arms. It was also reported by another laboratory that IL-1ra is increased in the lesional skin of psoriatic patients. This study was designed to measure the contents of IL-1α and IL-1ra in non-lesional and pathological SC obtained from inflammatory skin diseases including psoriasis and non-psoriatic dermatoses such as atopic dermatitis. The SC materials were obtained with a noninvasive tape-stripping method. Their soluble fractions were prepared and assayed for IL-1α and IL-1ra by enzyme-linked immunosorbent assays. As a result we confirmed the previous findings that the ratio of IL-1ra to IL-1α in the normal SC was much higher in the face than in the sun-protected sites, the trunk as well as extremities. Next, we found that IL-1α contents were significantly reduced in the SC samples obtained from inflammatory skin regardless of whether their IL-1ra contents increased or unchanged. Moreover, we noted that an increased ratio of IL-1ra to IL-1α in the SC was not specific to psoriasis, but was also found in other inflammatory skin diseases including atopic dermatitis. This ratio was found to become lower after successful treatment of these skin lesions with topical glucocorticoids. We conclude from these observations that the increased ratio of IL-1ra to IL-1α in the SC is a non-specific phenomenon that can occur in any inflammatory skin diseases regardless of the inflammatory pattern, probably reflecting a skin regulation process against various kinds of inflammation.