Levels of skin-derived antileukoproteinase (SKALP)/elafin in serum correlate with disease activity during treatment of severe psoriasis with cyclosporin A

Psoriasis: What Is New in Markers of Disease Severity?

Introduction. Psoriasis is a chronic inflammatory skin disease and is the result of the interaction between numerous external and internal factors. Psoriasis presents a wide range of skin manifestations encompassing individual lesions varying from pinpoint to large plaques that can evolve into generalised forms. The lesions mirror the pathophysiological mechanisms involved in psoriasis pathogenesis, such as inflammation, dysregulation of immune response, uncontrolled proliferation of keratinocytes and angiogenesis. In this article, we present the latest advances achieved regarding markers that correlate with psoriasis severity. Material and method. We have performed a narrative review on markers of psoriasis severity, including articles published between March 2018-March 2023. Results. We have identified four categories of markers: inflammation markers, oxidative stress markers, hormonal markers and cancer-related markers. The main focus was on inflammation biomarkers, including immunomodulatory molecules, haematological parameters, inflammatory cells and costimulatory molecules. Conclusions. The analysed data indicate that markers associated with inflammation, oxidative stress and hormones, and cancer-related markers could be useful in assessing the severity of psoriasis. Nevertheless, additional research is required to ascertain the practical importance of these biomarkers in clinical settings.

Severity, heterogeneity and systemic inflammation in psoriasis

Psoriasis may express as active severe disease or as mild stable disease. In particular, patients with active severe disease present systemic involvement, including comorbidities and increased values of parameters reflecting an active state of innate immunity. In contrast, patients with mild stable disease show a dominancy of acquired immunity. In this review article, we report the clinical aspects of disease manifestations of both active and quiescent psoriasis as well as the immunological aspects, as well as the impact on antimicrobial resistance. The activity of psoriasis is not captured in the present outcome measures for severity assessment. The present review suggests that incorporating disease activity may be important in the assessment of the efficacy of treatments.

High Expression and Clinical Significance of Elafin in Colorectal Cancer

OBJECTIVE

The decrease of Elafin is associated with several inflammatory diseases. Exogenous Elafin may be a treatment for IBD. Little data has shown the expression of Elafin in patients of colorectal cancer. Here, we tried to explore Elafin expression in human tissues of colorectal cancer.

METHODS

We examined the protein expression of Elafin in human tissues of adjacent nontumor and colorectal tumor by immunohistochemistry (IHC) or quantitative real-time polymerase chain reaction (qRT-PCR), then analyzed the clinical and RNA-seq data presented in The Cancer Genome Atlas (TCGA) database to confirm the relationship between Elafin levels and colorectal tumor.

RESULTS

Of the 88 paired samples, 68 colorectal cancer tissues indicated a high expression of Elafin compared with 52 matched adjacent noncancerous tissues. And the mRNA levels of Elafin in 35 paired tissues showed a similar trend. The RNA-seq and clinical data were available in 438 colorectal cancer tissues and 41 normal tissues in TCGA database. The RNA-seq data showed that Elafin mRNA was upregulated about twofold in colorectal cancer samples as compared to adjacent noncancerous samples (176.42 ± 402.13 vs. 96.75 ± 150.07; P = 0.208). No statistically significant correlation was found between the Elafin expression and the age, gender, tumor invasive stage, lymph node metastasis, and distant metastasis both at the protein and mRNA levels. However, the Elafin expression was correlated with clinical stage based on the AJCC guidelines at protein levels but not mRNA levels.

CONCLUSIONS

Elafin was upregulated in patients of colorectal cancer, resulting to potential limitations for exogenous Elafin treatment.

Serum elafin as a potential inflammatory marker in psoriasis

BACKGROUND

Psoriasis is a distressing chronic skin disease. Its exact pathogenesis is still unclear, as many factors interplay in its occurrence.

AIM

The aim of the study is to estimate elafin levels in the serum of both cases and controls and to correlate the levels with psoriasis severity and other markers of inflammation.

SUBJECTS AND METHODS

Twenty-six psoriatic cases along with 26 healthy controls were assigned in this case-control study. Psoriasis severity was determined by Psoriasis Area and Severity Index score. Elafin levels were measured by ELISA in serum of both cases and controls. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were measured in the cases.

RESULTS

Elafin levels show highly statistical significance difference (P < 0.001) between cases and controls. There is a statistical significant correlation between elafin levels and both psoriasis severity and inflammation markers as CRP and ESR.

CONCLUSION

Elafin represents a mirror for psoriasis severity and inflammatory state.

Picea mariana polyphenolic extract inhibits phlogogenic mediators produced by TNF-α-activated psoriatic keratinocytes: Impact on NF-κB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Picea mariana ((Miller) Britton, Sterns, and Poggenburg; Pinaceae) bark has been traditionally used by North American natives for treating topical inflammations. It has been also suggested to improve various inflammatory skin disorders like Psoriasis vulgaris. Extracts from this bark storage protein contain polyphenolic compounds which have well-known antiinflammatory activities. Based on the capacity of polyphenolic compounds to modulate functions of normal human keratinocytes, this study was set up to decipher the mechanisms of action of a chemically characterized polyphenolic extract from Picea mariana bark (BS-EAcf) on lesional keratinocytes of skin with psoriasis vulgaris, a disease driven by the immune system in which TNF-α plays a significant role.

MATERIALS AND METHODS

BS-EAcf corresponds to the ethyl acetate soluble fraction from the hot water extract of Picea mariana bark. BS-EAcf effects were evaluated in normal human (NHK) and psoriatic (PK) keratinocytes stimulated by TNF-α. Cell viability was assessed by lactate deshydrogenase release and propidium iodide (PI) staining. The mechanisms of action of BS-EAcf in keratinocytes were investigated by flow cytometry, ELISAs, RT-PCR and western blot analyses.

RESULTS

PK exhibited a higher response to TNF-α than NHK regarding the ICAM-1 expression and the production of NO, IL-6, IL-8, fractalkine and PGE2, whereas BS-EAcf significantly inhibited this TNF-α-induced increase at concentrations without causing keratinocyte toxicity. Additionally, this extract significantly inhibited the TNF-α-induced release of elafin and VEGF by PK and NHK. Since TNF-α activation of most of these factors is dependent on the NF-κB pathway, this latter was studied in TNF-α-activated PK. BS-EAcf inhibited the TNF-α-induced phosphorylation and degradation of total IκBα as well as phosphorylation of NF-κB p65.

CONCLUSIONS

The ethyl acetate fraction from Picea mariana bark extract showed inhibitory effects of cytokines, chemokines, adhesion molecules, nitric oxide and prostaglandins produced by keratinocytes under TNF-α activation through down-regulating the NF-κB pathway. This study demontrated that this extract could be a potential antiinflammatory agent capable of improving psoriatic skin.

Therapeutic potential of human elafin

Elafin is an endogenous human protein composed of an N-terminal transglutaminase substrate motif and a C-terminal WAP (whey acidic protein)-domain with antiproteolytic properties. Elafin is expressed predominantly in epithelial tissue and potently inhibits the neutrophil-derived serine proteases elastase and proteinase-3 by a competitive tight-binding mechanism. Furthermore, it inhibits EVE (endogenous vascular elastase). Studies on several animal models show that antiprotease augmentation with human elafin is an effective strategy in the treatment of inflammatory vascular, systemic and pulmonary diseases and of inflammation triggered by reperfusion injury. This raises the possibility that elafin might be effective in the treatment of a variety of human inflammatory diseases. In a Phase I clinical trial, elafin was well tolerated. Phase II trials are underway to investigate the therapeutic effects of elafin on post-operative inflammation and the clinical consequences of major surgery. Of particular interest is the reduction of post-operative morbidity after oesophagus cancer surgery, coronary artery bypass surgery and kidney transplantation.

Gene expression profiling in psoriatic scalp hair follicles: clobetasol propionate shampoo 0.05% normalizes psoriasis disease markers

BACKGROUND

Clobetasol propionate shampoo is effective and safe in treatment of scalp psoriasis (SP). Gene expression profiling of psoriatic skin biopsies led to the identification of numerous disease-related genes. However, it remained unknown whether the gene expression profile of hair follicles of SP patients was also affected.

OBJECTIVES

To determine whether psoriasis-related genes are differentially regulated in the hair follicles of SP patients and whether the modulation of these genes can be correlated with clinical severity scores.

METHODS

A single arm, open study was conducted in three centres. SP patients received daily treatment with clobetasol propionate shampoo. At Baseline, Weeks 2 and 4, investigators assessed clinical severity parameters and collected scalp hair follicles in anagen phase. Total RNA extracted from hair follicles was used to determine the expression level of 44 genes, which were reported previously to be upregulated in the skin of psoriasis patients.

RESULTS

RNA of good quality and sufficient quantity was obtained from hair follicles of psoriasis patients and healthy volunteers (HV). The expression level of 10 inflammation-related genes was significantly increased in psoriatic hair follicles. The patient's exploratory transcriptomic score, defined as the mean fold modulation of these 10 genes compared with HV, correlated with clinical severity scores. Clobetasol propionate shampoo was effective in decreasing both the exploratory transcriptomics and the clinical severity scores.

CONCLUSION

Hair follicles of SP patients are affected by the inflammatory process. The change in the expression level of inflammation-related genes correlates with the severity of the disease.

Elafin is a biomarker of graft-versus-host disease of the skin

Graft-versus-host disease (GVHD), the major complication of allogeneic bone marrow transplantation, affects the skin, liver, and gastrointestinal tract. There are no plasma biomarkers specific for any acute GVHD target organ. We used a large-scale quantitative proteomic discovery procedure to identify biomarker candidates of skin GVHD and validated the lead candidate, elafin, with enzyme-linked immunosorbent assay in samples from 492 patients. Elafin was overexpressed in GVHD skin biopsies. Plasma concentrations of elafin were significantly higher at the onset of skin GVHD, correlated with the eventual maximum grade of GVHD, and were associated with a greater risk of death relative to other known risk factors (hazard ratio, 1.78). We conclude that elafin has significant diagnostic and prognostic value as a biomarker of skin GVHD.

Proteases and antiproteases in chronic neutrophilic lung disease - relevance to drug discovery

Chronic inflammatory lung diseases such as cystic fibrosis and emphysema are characterized by higher-than-normal levels of pulmonary proteases. While these enzymes play important roles such as bacterial killing, their dysregulated expression or activity can adversely impact on the inflammatory process. The existence of efficient endogenous control mechanisms that can dampen or halt this overexuberant protease activity in vivo is essential for the effective resolution of inflammatory lung disease. The function of pulmonary antiproteases is to fulfil this role. Interestingly, in addition to their antiprotease activity, protease inhibitors in the lung also often possess other intrinsic properties that contribute to microbial killing or termination of the inflammatory process. This review will outline important features of chronic inflammation that are regulated by pulmonary proteases and will describe the various mechanisms by which antiproteases attempt to counterbalance exaggerated protease-mediated inflammatory events. These proteases, antiproteases and their modifiers represent interesting targets for therapeutic intervention.

Beta-defensin-2 protein is a serum biomarker for disease activity in psoriasis and reaches biologically relevant concentrations in lesional skin

BACKGROUND

Previous studies have extensively documented antimicrobial and chemotactic activities of beta-defensins. Human beta-defensin-2 (hBD-2) is strongly expressed in lesional psoriatic epidermis, and recently we have shown that high beta-defensin genomic copy number is associated with psoriasis susceptibility. It is not known, however, if biologically and pathophysiologically relevant concentrations of hBD-2 protein are present in vivo, which could support an antimicrobial and proinflammatory role of beta-defensins in lesional psoriatic epidermis.

METHODOLOGY/PRINCIPAL FINDINGS

We found that systemic levels of hBD-2 showed a weak but significant correlation with beta defensin copy number in healthy controls but not in psoriasis patients with active disease. In psoriasis patients but not in atopic dermatitis patients, we found high systemic hBD-2 levels that strongly correlated with disease activity as assessed by the PASI score. Our findings suggest that systemic levels in psoriasis are largely determined by secretion from involved skin and not by genomic copy number. Modelling of the in vivo epidermal hBD-2 concentration based on the secretion rate in a reconstructed skin model for psoriatic epidermis provides evidence that epidermal hBD-2 levels in vivo are probably well above the concentrations required for in vitro antimicrobial and chemokine-like effects.

CONCLUSIONS/SIGNIFICANCE

Serum hBD-2 appears to be a useful surrogate marker for disease activity in psoriasis. The discrepancy between hBD-2 levels in psoriasis and atopic dermatitis could explain the well known differences in infection rate between these two diseases.

A genome-wide expression analysis in blood identifies pre-elafin as a biomarker in ARDS

Previous microarray-based studies of acute respiratory distress syndrome (ARDS) were performed using various models to mimic disease pathogenesis. The complexity of the pathophysiologic response to direct or indirect lung injury in ARDS is difficult to reconstruct in experimental conditions. Thus, direct analysis of ARDS patient blood may provide valuable information. We investigated genome-wide gene expression profiles in paired whole blood samples from patients with ARDS (n = 8) during the acute stage (within 3 d of diagnosis) and recovery stage of ARDS (around ICU discharge). Among 126 differentially expressed genes, peptidase inhibitor 3 (PI3, encoding elafin, a potent neutrophil elastase inhibitor) had the largest fold-change (-3-fold changes, acute stage/recovery stage) in expression, indicating down-regulation during the acute stage of ARDS. We further examined plasma PI3 levels in 40 patients with ARDS and 23 at-risk control subjects from the same cohort. There was a coincidence of the microarray findings of lower PI3 gene expression with the lower plasma PI3 during the acute-stage. The plasma PI3 levels were statistically significant different among pre-diagnosis, day of diagnosis, and post-diagnosis groups (ANOVA, P = 0.001), with a trend of decreasing from pre- to post-diagnosis group. The time course of plasma PI3 decrease is well correlated with the course of early ARDS development (Pearson correlation coefficient: -0.52, P = 0.0006). Considering that PI3 can covalently binding to extracellular matrix in lung, circulating PI3 may provide a useful clinical marker for monitoring the early development of ARDS and may have implications for ARDS treatment.

Identification of avarol derivatives as potential antipsoriatic drugs using an in vitro model for keratinocyte growth and differentiation

Avarol, a marine sesquiterpenoid hydroquinone, and 14 avarol derivatives have shown interesting anti-inflammatory properties in previous studies. In this study, avarol and derivatives were evaluated in high-throughput keratinocyte culture models using cytokeratin 10 and SKALP/Elafin expression as markers for respectively normal and psoriatic differentiation. Avarol and five of its derivatives (5, 10, 13, 14 and 15) were selected for further study. Only 10, 13, 14 and 15 were able to inhibit keratinocyte cell growth. Changes in expression levels of 22 genes were assessed by quantitative real time PCR (qPCR). From these genes, TNFalpha mRNA levels showed the strongest changes. For compound 13, 15 and dithranol (used as a model antipsoriatic drug), a dose-dependent downregulation of TNFalpha mRNA was found. The changes in TNFalpha mRNA were confirmed at the protein level for compound 13. Additionally, this compound was able to reduce also IL-8 and COX-2 mRNA levels and this effect was correlated with a reduction in COX-2 protein expression. The mechanism of action of this compound involves at least the inhibition of NF-kappaB-DNA binding activity. In conclusion, our high-throughput screening models in combination with quantitative assessment of changes in gene expression profiles identified the avarol derivative 13, a benzylamine derivative of avarol at the 4' position of benzoquinone ring, as an interesting anti-psoriatic drug candidate that inhibits keratinocyte cell growth and TNFalpha and COX-2 expression.

Gene expression profiles in psoriasis: analysis of impact of body site location and clinical severity

BACKGROUND

Psoriasis is characterized by symmetry of plaques and modulation of multiple genes within those plaques.

OBJECTIVES

We compared gene expression profiles of plaques of psoriasis at different anatomical sites for both symmetrical and asymmetrical disease to ascertain whether the same genes were expressed.

METHODS

Gene expression profiles were analysed in biopsies from lesional and uninvolved skin from two groups of patients with either predominantly symmetrical or truncal plaques of psoriasis vulgaris, and from normal skin of healthy volunteers. Genomic analyses were performed using cDNA array and kinetically monitored reverse transcriptase-initiated polymerase chain reaction (kRT-PCR) approaches. A cluster of genes upregulated in involved psoriasis skin as compared with normal skin was identified using each of these two technologies.

RESULTS

Clustering of patients based on their gene expression profile did not reveal any correlation with family history of psoriasis, age at onset or association of psoriasis with arthritis. There was no difference in gene expression profile between the type (symmetrical vs. truncal) or location (left vs. right side of body) of psoriatic plaques. Gene expression profiles of involved psoriatic skin analysed by kRT-PCR analysis did correlate with both global (Psoriasis Area and Severity Index) and local (erythema, desquamation and plaque elevation) clinical severity.

CONCLUSIONS

These results indicate that it may be feasible to analyse the molecular effects of pharmacological agents on psoriatic skin in 'minizone' protocols, that the obtained data can be correlated with clinical severity and that plaques of psoriasis in the same individual express the same genes.

SPINK5 and Netherton Syndrome: Novel Mutations, Demonstration of Missing LEKTI, and Differential Expression of Transglutaminases

Netherton syndrome (NTS) is an autosomal recessive congenital ichthyosis featuring chronic inflammation of the skin, hair anomalies, epidermal hyperplasia with an impaired epidermal barrier function, failure to thrive and atopic manifestations. The disease is caused by mutations in the SPINK5 gene encoding the serine proteinase inhibitor lympho-epithelial Kazal-type inhibitor (LEKTI). Sequence analyses of SPINK5 in seven NTS patients from five different families allowed us to identify two known and three novel mutations all creating premature termination codons. We developed a monoclonal antibody giving a strong signal for LEKTI in the stratum granulosum of normal skin and demonstrated absence of the protein in NTS epidermis. Immunoblot analysis revealed presence of full length LEKTI and of LEKTI cleavage fragments in normal hair roots, whereas in NTS hair roots LEKTI and its cleavage products were completely missing. Transglutaminase1 activity was present throughout almost the entire suprabasal epidermis in NTS, whereas in normal skin it is restricted to the stratum granulosum. In contrast, immunostaining for transglutaminase3 was absent or faint. Moreover, comparable with the altered pattern in psoriatic skin the epidermis in NTS strongly expressed the serine proteinase inhibitor SKALP/elafin and the anti-microbial protein human beta-defensin 2. These studies demonstrate LEKTI deficiency in the epidermis and in hair roots at the protein level and an aberrant expression of other proteins, especially transglutaminase1 and 3, which may account for the impaired epidermal barrier in NTS.

Low dose cyclosporin A treatment in generalized pustular psoriasis

Generalized pustular psoriasis is a rare form of psoriasis, seldom seen in children. Three patients with generalized pustular psoriasis are presented, two of whom were a sister and brother and whose grandfather also had pustular psoriasis. Lesions consisted of pustular, erythematous, scaly, follicular papules located on the trunk, scalp, and extremities. The pustules in some areas coalesced to form lakes. Histologic examination of several biopsy specimens revealed the changes of pustular psoriasis, which were parakeratosis, elongation of the rete ridges, and deep spongioform pustules and Munro abscesses. All patients were treated with cyclosporin A for periods of 2-12 months. The doses ranged from 1 to 2 mg/kg/day. Clearance of psoriatic lesions occurred after 2-4 weeks of therapy.

Elafin is induced in epidermis in skin disorders with dermal neutrophilic infiltration: interleukin-1 beta and tumour necrosis factor-alpha stimulate its secretion in vitro

BACKGROUND

Elafin, an elastase inhibitor produced by keratinocytes, is overexpressed in the subcorneal region of skin affected by psoriasis, a major feature of which is epidermal infiltration by neutrophil leucocytes.

OBJECTIVES

We studied the expression of elafin in the epidermis in other skin disorders characterized by dermal neutrophil infiltration and in skin disorders with dermal lymphocyte infiltration.

PATIENTS/METHODS

We examined biopsies from the lesional skin of patients with Behçet's syndrome, Sweet's syndrome, pyoderma gangrenosum, cutaneous allergic vasculitis and acute bacterial infection (cellulitis), and from the skin of patients with chronic prurigo, discoid lupus erythematosus and psoriasis. We performed in vitro experiments using cultured keratinocytes treated with mediators such as interleukin (IL)-1 beta, tumour necrosis factor (TNF)-alpha, IL-6, neutrophil elastase and interferon (IFN)-gamma.

RESULTS

Anti-elafin antibody showed a strong reaction with the subcorneal region of the epidermis in patients with Behçet's syndrome, Sweet's syndrome, pyoderma gangrenosum, cutaneous allergic vasculitis and acute bacterial infection (cellulitis), but showed no reaction in skin from patients with dermal lymphocyte infiltration such as is seen in chronic prurigo and discoid lupus erythematosus. The in vitro experiments demonstrated that treatment with IL-1 beta and TNF-alpha resulted in 2.6-fold and 4-fold stimulation of elafin secretion, respectively, whereas IL-6, neutrophil elastase and IFN-gamma caused no significant changes in elafin release.

CONCLUSIONS

These results suggest that inflammatory mediators such as IL-1 beta or TNF-alpha secreted by dermal neutrophils may be involved in overexpression of elafin in keratinocytes; this could protect the epidermis from degradation by dermal neutrophil infiltration.

Identification, origins and the diurnal role of the principal serine protease inhibitors in human tear fluid

PURPOSE

Previous work identified polymorphonuclear leukocyte (PMN) elastase as the major caseinolytic entity in tears collected after overnight eye closure. This study was designed to identify the principal serine protease inhibitors (serpins) in tears and to determine their function in the regulation of PMN cell proteases on eye closure.

METHODS

Reflex and closed eye tear samples were collected by microcapillary tube and centrifuged. After reflex and closed eye supernatants (R and C) were fractionated by HPLC, samples were subjected to casein zymography and reverse zymography. Western blots were utilized to screen tears and HPLC fractions for elastase, cathepsin G and proteinase-3 and to obtain semi-quantitative data on alpha 1-protease inhibitor (alp1), alpha 1-antichymotrypsin (alpha 1-Achy), secretory leukocyte protease inhibitor (SLPI), elafin and alpha 2-macroglobulin (alpha 2-M) as well as associated complexes and products. To confirm specificity of reactivity, samples were immunoprecipitated for a given protease or serpin and screened for the coprecipitation of interacting species.

RESULTS

Although R fluid contains no caseinolytic activity, it contains low levels of serpin-like activity principally in the form of SLPI (5-10 ng/microliter). Lesser amounts of alpha 2-M, alpha 1-Achy and alp1 (approximately < 1-3 ng/microliter) are also evident. C fluid is associated with very high levels of PMN cell proteases along with a approximately 5-20-fold increase in the concentrations of all of the above inhibitors. Trace levels of elafin were also detected. The concentrations of rapid reacting inhibitors exceeded that of proteases, with SLPI, alpha 1-Achy and alp1 being the principal functional entities. In atypical samples, complexes of elastase and alpha 2-M were also encountered.

CONCLUSIONS

SLPI, a known antimicrobial agent and an elastase and cathepsin G inhibitor, is the principal serpin in R fluid. C fluid is associated with a marked increase in the concentrations of an array of rapid reacting serpins capable of inhibiting all known PMN cell serine proteases. In the normal closed eye, the concentration of rapid reacting inhibitors always exceeds that of proteases with C fluid also containing a functional reserve of the slow reacting inhibitor alpha 2-M.

Identification and sequence analysis of two new members of the SKALP/elafin and SPAI-2 gene family. Biochemical properties of the transglutaminase substrate motif and suggestions for a new nomenclature

The human epithelial proteinase inhibitor SKALP/elafin and the porcine sodium-potassium ATPase inhibitor SPAI-2 are two highly homologous proteins that share an NH2-terminal transglutaminase substrate domain and a COOH-terminal whey acidic protein (WAP) domain. Here we describe the bovine and simian orthologs of SKALP/elafin as well as two new bovine family members that are designated Trappin-4 and Trappin-5 on the basis of a new nomenclature that we propose (Trappin = TRansglutaminase substrate and WAP motif-containing ProteIN). Sequence analysis of Trappin-4 and Trappin-5 revealed a domain structure that is very similar to SPAI-2 (Trappin-1) and SKALP/elafin (Trappin-2). The transglutaminase substrate motifs are conserved although the number of repeats varies among species and among family members. The sequence of Trappin-4 and Trappin-5 diverges from Trappin-1 and Trappin-2 at the putative reactive site in the WAP domain. The bovine ortholog of Trappin-2 is expressed in tongue and snout epidermis; Trappin-4 is expressed in trachea, ileum, and tongue; and Trappin-5 is expressed at low levels in trachea, as determined by RNase protection and Northern blot analysis. Based on the analysis of 67 transglutaminase substrate repeats as present in all known Trappin gene family members from four different mammalian species a consensus sequence could be established: Gly-Gln-Asp-Pro-Val-Lys (GQDPVK). Using biotinylated hexapeptide probes we found that the GQDPVK sequence is a very efficient transglutaminase substrate both for guinea pig liver transglutaminase and for epidermal transglutaminase, and it acts as acyl donor as well as acceptor. We propose that the Trappin protein family forms a new group of enzyme inhibitors with various specificities of the WAP domain, which share transglutaminase substrate motifs that can act as an anchoring sequence.

Skin-derived antileukoproteinase (SKALP) is decreased in pustular forms of psoriasis. A clue to the pathogenesis of pustule formation?

Skin-derived antileukoproteinase (SKALP, also known as elafin) is an inducible epidermal serine proteinase inhibitor, that we have recently characterized at the protein and DNA levels. SKALP is a strong and specific inhibitor of PMN elastase, and is putatively involved in the regulation of cutaneous inflammatory processes. In order to investigate the role of SKALP in the control of elastase in psoriatic epidermis, we compared SKALP expression in normal skin, and in skin from patients with chronic plaque psoriasis and pustular forms of psoriasis. Epidermal scales and biopsies were collected and SKALP expression was studied at the mRNA level and at the protein level both functionally and immunochemically. In epidermal scales, we found that the levels of both free and total SKALP activity in pustular psoriasis were far lower than in plaque psoriasis. A significant number of pustular psoriasis patients showed latent SKALP activity, which represents the amount of SKALP putatively complexed to elastase. In addition, we found free elastase activity in 25% of the pustular psoriasis patients, indicating a total saturation of epidermal SKALP activity. In epidermal biopsies from pustular psoriasis patients, SKALP activity was significantly decreased compared with those from plaque psoriasis patients. Northern blot analysis did not reveal differences in epidermal mRNA levels between chronic plaque psoriasis and pustular psoriasis. We hypothesize that a reduced amount of epidermal SKALP contributes to an imbalance between elastase and its inhibitor, thereby promoting the formation of epidermal pustules. We suggest that these findings could provide a rationale for the treatment of pustular psoriasis with inhibitors of PMN-derived proteinases, as a new therapeutic modality.

Expression of SKALP/elafin during wound healing in human skin

Skin-derived antileukoproteinase (SKALP), also known as elafin, is a proteinase inhibitor with specificity for polymorphonuclear leucocyte (PMN)- derived elastase and proteinase-3. SKALP is absent in normal human epidermis, but is strongly induced in inflammatory dermatoses such as psoriasis. SKALP is putatively involved in the regulation of cutaneous inflammation by inhibiting PMN derived proteinases. The aim of this study was to investigate SKALP expression and PMN infiltration during wound healing in human skin. This was examined in healing excisional wounds in normal skin and in impaired healing in various types of chronic venous ulcers. Tissues were analysed using immunohistochemistry and Northern blot analysis. Healing of excisional wounds was studied from day 0 to day 14. An influx of PMN was seen rapidly after wounding and was maximal between day 2 and 4 and then subsided. SKALP was induced within 48 h and was expressed in the suprabasal keratinocytes of the wound edge and the migrating epidermal sheet. SKALP expression was maximal on day 4 and was downregulated at the time of complete reepithelialization (7-14 days). In venous ulcers, PMN were abundant in the wound bed and scarce under the wound edge. SKALP was strongly expressed in the keratinocytes of the wound edge in all types of ulcers studied. In the wound bed, SKALP was not detectable. Our results suggest that SKALP plays a role in the acute, inflammatory phase of wound healing. From the kinetics and topology of SKALP expression we surmise that it negatively regulates PMN infiltration.