Enzymatic activity of desquamin

Immunopathogenesis of oropharyngeal candidiasis in human immunodeficiency virus infection

Oropharyngeal and esophageal candidiases remain significant causes of morbidity in human immunodeficiency virus (HIV)-infected patients, despite the dramatic ability of antiretroviral therapy to reconstitute immunity. Notable advances have been achieved in understanding, at the molecular level, the relationships between the progression of HIV infection, the acquisition, maintenance, and clonality of oral candidal populations, and the emergence of antifungal resistance. However, the critical immunological defects which are responsible for the onset and maintenance of mucosal candidiasis in patients with HIV infection have not been elucidated. The devastating impact of HIV infection on mucosal Langerhans' cell and CD4(+) cell populations is most probably central to the pathogenesis of mucosal candidiasis in HIV-infected patients. However, these defects may be partly compensated by preserved host defense mechanisms (calprotectin, keratinocytes, CD8(+) T cells, and phagocytes) which, individually or together, may limit Candida albicans proliferation to the superficial mucosa. The availability of CD4C/HIV transgenic mice expressing HIV-1 in immune cells has provided the opportunity to devise a novel model of mucosal candidiasis that closely mimics the clinical and pathological features of candidal infection in human HIV infection. These transgenic mice allow, for the first time, a precise cause-and-effect analysis of the immunopathogenesis of mucosal candidiasis in HIV infection under controlled conditions in a small laboratory animal.

Variability of enzyme markers during clinical regression of atopic dermatitis

Skin surface enzyme activities were found to be significantly different in healthy and in skin with atopic dermatitis and, following appropriate treatment, a close correlation was observed between the clinical staging of the atopic dermatitis and the levels of the assayed marker enzymes. Samples were taken, by stripping with simple adhesive tapes, from a group of subjects on cure in a spa. The corneocytes were recovered from the first layers of the stratum corneum. Aqueous extracts of the strips were tested for their activity on chromophoric substrates which allow fluorescence spectrometry to be used to assay the trypsin-like, acid-phosphatase-like and phospholipase-A2-like activities. We show that the restoration of return to activities close to those of healthy subjects is related to the general condition of the patients, who showed a clearly improved SCORAD. Recovery of the trypsin-like activity and attenuation of the phospholipase-like activity, paralleled the regression of the dermatitis as assessed by a decrease in clinically evaluated parameters of xerosis and inflammation.

A zymogel enhances the self-cleaning abilities of the skin of the pilot whale (Globicephala melas)

Enzyme activity in the stratum corneum of the pilot whale Globicephala melas was investigated employing colorimetric enzyme screening assays combined with NATIVE PAGE, size exclusion chromatography (SEC) and histochemical staining procedures. Applying different substrates, several enzymes were detected. The histochemical demonstration of some selected hydrolytic enzymes enriched in the stratum corneum showed high extracellular accumulation. As demonstrated by size exclusion chromatography, high molar mass aggregates were built up from a glycoprotein-rich 20-30-kD fraction. Using NATIVE PAGE experiments under non-reducing conditions, a selection of five degrading enzymes was recovered within the above-reported aggregates. Activity of extracellular aggregate-attached enzymes in the superficial layer of the stratum corneum exhibited no remarkable decrease potentially resulting from self-degradation. We thus conclude that due to their enclosure within the microenvironment of aggregates, a zymogel is formed and autolysis of the stratum corneum is reduced. With respect to the skin surface, the zymogel with hydrolytic activities covering major parts of it enhances the self-cleaning abilities of the skin of the pilot whale based on physical pre-requisites by hydrolyzing adhesive glycoconjugates of settling biofouling organisms considered as primary steps in fouling.

Epidermal enzymes: their role in homeostasis and their relationships with dermatoses

This review underlines the importance of different enzymes (beta-glucocerebrosidase, phospholipase A2, proteases and cholesterol sulfatase) in the formation and maintenance of the epidermal barrier function. Certain diseases may be characterized by the lack or excess of one or more of these different enzyme activities, altering the homeostatic equilibrium of the epidermis. In addition to this, particular enzymes may show potential in the development of novel dermocosmetic strategies.

Response of keratinocytes from normal and psoriatic epidermis to interferon-gamma differs in the expression of zinc-alpha(2)-glycoprotein and cathepsin D

Psoriasis is a T cell-mediated inflammatory disease characterized by hyperproliferation and by aberrant differentiation. We found cathepsin D and zinc-alpha(2)-glycoprotein, two catalytic enzymes associated with apoptosis and desquamation, to be present in the stratum corneum of the normal epidermis but absent from the psoriatic plaque. Psoriasis is characterized by an altered response to interferon-gamma (IFN-gamma), including the induction of apoptosis in normal but not in psoriatic keratinocytes, often with opposite effects on gene expression of suprabasal proteins. We found that IFN-gamma binding and signaling were attenuated in psoriasis: The IFN-gamma receptor, the signal transducer and activator of transcription STAT-1, and the interferon regulatory factor IRF-1 were strongly up-regulated by IFN-gamma in normal keratinocytes, but not in psoriatic ones. IFN-gamma strongly up-regulated the expression of the catalytic enzymes cathepsin D and zinc-alpha(2)-glycoprotein in normal keratinocytes but down-regulated them in psoriatic ones; the reverse was true of the apoptotic suppressor bcl-2. We believe that the aberrant response to IFN-gamma plays a central role in the pathophysiology of psoriasis, particularly the disruption of apoptosis and desquamation.

Protein oxidation in human stratum corneum: susceptibility of keratins to oxidation in vitro and presence of a keratin oxidation gradient in vivo

The stratum corneum is located at the interface between body and environment and thus is constantly exposed to a pro-oxidative environment. Previously, we have demonstrated that stratum corneum lipids are targets of oxidative stress induced by ozone and by ultraviolet A and B exposure. Here, we employed an immunoblotting technique to detect protein oxidation in human stratum corneum obtained by tape stripping. After lysis, protein carbonyl groups were measured by derivatization with dinitrophenylhydrazine, separation by sodium dodecylsulfate-polyacrylamide gel electrophoresis, and immunoblotting using antibodies against dinitrophenyl groups. Keratin 10, identified by use of specific antibodies and by microsequencing, was demonstrated in vitro to be oxidizable by ultraviolet A irradiation, hypochlorite, and benzoyl peroxide. In vivo, a keratin 10 oxidation gradient with low levels in the lower stratum corneum layers, and about 3-fold higher contents of carbonyl groups towards the outer layers was demonstrated in forehead stratum corneum of healthy volunteers (n = 6). As protein oxidation can be associated with an increased susceptibility to proteases, this finding may be important for better understanding the process of desquamation.

Role of endogenous cathepsin D-like and chymotrypsin-like proteolysis in human epidermal desquamation

Even though the skin surface is acidic (about pH 5), most in vitro studies on desquamation have been performed at alkaline pH. We demonstrate that the standard in vitro model system, which achieves squame shedding upon incubation of plantar stratum corneum for 1 day in an alkaline buffer that must include a chelating agent, can be extended to a more realistic model in which the incubation is for 4 days, at varying pHs from 5 to 8, without exogenous chelators. Desmoglein I from stratum corneum was degraded by the squames shed at pH 5 as well as at pH 8. Squame shedding was inhibited to varying extents by the addition of proteinase inhibitors, whose specificity suggested that the crucial enzymatic activity at pH 8 was a chymotrypsin-like serine proteinase, while a similar activity at pH 5 was accompanied by an aspartic proteinase activity of comparable strength. Four degradation peaks were observed when the insulin B chain was reacted with shed squames at pH 5. Two of these peptides were suppressed by the addition of phenylmethylsulphonyl fluoride, the other two by pepstatin A; chymostatin inhibited all four, but E-64 and leupeptin showed no effect. The implied specificity was confirmed by reacting the insulin (without squames) with the standard enzymes human liver cathepsin D and pancreatic chymotrypsin, reproducing the expected degradation products. These results suggest that epidermal desquamation at acidic pH requires two proteolytic activities, one of which is an analogue of chymotrypsin and the other of cathepsin D. Endogenous proteinases corresponding to these activities have been previously identified, namely the stratum corneum chymotryptic enzyme and the mature active form of cathepsin D.

Release of amino acids, fluorescamine-reactive substances and substance P from the epidermis of the living animal

The present study demonstrates a procedure for extraction and determination of stratum corneum amines in the living animal. A nonleaky well, containing 10 mM Tris-HCl buffer, pH 7.0, was constructed on the shaved backs of anesthetized animals. It was found that Ser, Ala, Gly and Pro are mainly released from the stratum corneum of 4-month-old guinea pigs, and in 2-month-old rats, Gly, Ser and Arg show the highest degree of release. Much lower amino acid concentrations were observed in 20-month-old rats. This was also reflected by the high levels of fluorescamine-reactive substances released from young rat skin as compared to the old animals. The release of the neuropeptide substance P into the aqueous medium was increased 3.2 times upon heat stimulus as compared to control skin. Amines and other compounds released from the skin may serve as markers for skin aging or for certain skin disorders, leading to a new approach for their treatments.

Isoforms of cathepsin D and human epidermal differentiation

Cathepsin D is an ubiquitously expressed lysosomal aspartic proteinase, with well-determined structural and chemical properties but a less clearly defined biological role. In stratified epithelia, the chronology of cathepsin D activation and degradation can be connected with stages of cellular differentiation. We partially purified cathepsin D from human epidermis and from separated stratum corneum by standard biochemical procedures, monitored by SDS-PAGE and Western blotting, and verified its identity as to molecular mass, pH optimum, N-terminal sequencing, reactivity with the specific antibody, inhibition by pepstatin A, and specific enzyme activity. It had hemoglobin-degrading activity over the acid range, with maximum at pH 3. It also degraded bovine serum albumin, human keratins, and stratum corneum extracts at pH 4. We discerned all three isoforms of human cathepsin D (the 52 kDa proenzyme and the active forms at 48 kDa and 33 kDa) in the epidermis; both active forms were also seen in the stratum corneum, but the proenzyme was not. Gene expression of cathepsin D in epidermal keratinocytes resembled that of suprabasal structural proteins (involucrin, keratin K10, transglutaminase) in its response to the calcium switch. An antibody to the 33 kda isoform immunolocalized to the granular layer and the stratum corneum (whereas antibodies to the 48 kDa isoform have been reported to stain mainly the upper spinous and granular layers). A plausible hypothesis to harmonize these results is that cathepsin D is first expressed as the proenzyme in the upper spinous layer, is activated in the lysosomes in the granular layer to the 48 kDa form, and is degraded to the 33 kDa form in the transition zone between the granular layer and the stratum corneum. As the stratum corneum is an acid environment, with an ambient pH of approximately 4.5, cathepsin D is available and suited to contribute to desquamation.

Desquamin is an epidermal ribonuclease

Desquamin is a glycoprotein that we have isolated from the upper granular layer and the stratum corneum of human epidermis; it is not ordinarily expressed in submerged cultures, whose terminal differentiation stops short of formation of these layers. The exogenous addition of desquamin to human cultured keratinocytes extended their maturation, and hematoxylin staining indicated a loss of cell nuclei. For confirmation, cultured cells were lysed in situ, and the nuclei were incubated with desquamin for several days, then stained with hematoxylin. Damage to the nuclei was evident: the nuclear inclusions remained intact, while the surrounding basophilic nuclear matrix was degraded. Desquamin was then tested directly for nuclease activity. Ribonuclease activity was determined by incubating desquamin with human epidermal total RNA and monitoring the dose-dependent disappearance of the 28S and 18S ribosomal RNA bands in an agarose/formaldehyde gel. On RNA-containing zymogels, we confirmed the RNase activity to be specific to desquamin. Using synthetic RNA homopolymers, we found the active RNase domains to be limited to cytosine residues. On the contrary, DNA was not degraded by an analogous procedure, even after strand-separation by denaturation.

30-kDa trypsin-like proteases in the plantar stratum corneum

The casein digestible proteases in human plantar stratum corneum were determined to be about 75-kDa, 30-kDa and 25-kDa in molecular weight by zymography. The enzymatic activity of the 75-kDa and 25-kDa proteases was specifically inhibited by chymostatin, which is an inhibitor of chymotrypsin-like serine proteases, and the proteases around 30-kDa were inhibited by leupeptin, a trypsin-like serine protease inhibitor. The enzymatic activity of all these proteases was inhibited by aprotinin. The 30-kDa trypsin-like proteases were heat-stable; their enzymatic activity still remained even after heating at 100 degrees C for 60 minutes. Their optimal pH was around 9, and the activity was higher in the outer part of the stratum corneum than in the inner part.

Disaggregation of corneocytes from surfactant-treated sheets of stratum corneum in hyperkeratosis on psoriasis, ichthyosis vulgaris and atopic dermatitis

To elucidate the pathogenesis of impaired barrier function and the influence of surfactant on the stratum corneum in hyperkeratosis, we investigated morphological alterations of the corneocytes with soap solution. Groups of five patients each with psoriasis vulgaris (PV), ichthyosis vulgaris (IV), atopic dermatitis (AD), and normal controls were examined. Four samples of the horny layer were obtained from the same site by cyanoacrylate adhesive biopsy. The first sample was used for the superficial layer, and the fourth, for the basal horny layers. Each sample was agitated in 1% stirred soap solution at 60 degrees C. The number and size of isolated corneocytes and the morphologic changes were investigated. The release of corneocytes was greater and the swelling and morphological changes of corneocytes exposed to soap solutions were less in PV and AD than in IV or in healthy subjects. In IV, the release was markedly less than in controls. The release and swelling were greater in the superficial than in the basal horny layers. It was concluded that the cohesiveness of corneocytes was probably less in PV and AD and greater in IV than in normals. It was also suggested that the cohesion of corneocytes from the superficial horny layer was less than that from the deep layer. The permeability of the cornified envelope in PV and AD patients was less than in IV or healthy subjects. It was confirmed that highly potent soaps induce loss of many corneocytes and reduce the barrier function of the stratum corneum.

Ultraviolet rays induced expression of lectins on the surface of a squamous carcinoma keratinocyte cell line

Human keratinocytic cells from squamous carcinoma (SCL-1) present, under resting conditions, relatively low amounts of endogenous lectins (sugar-binding proteins). Upon uv irradiation, they express on their cell surface large amounts of endogenous lectin molecules able to bind neoglycoproteins bearing either alpha-L-rhamnosyl or alpha-D-glucosyl residues. A similar binding specificity was found with normal human keratinocytes under the same culture conditions. At sunlike doses, uv.A (365 nm) was more efficient than uv.B (312 nm) in the expression of such receptors on the surface of SCL-1 cells. The increased presentation of lectins by SCL-1 cells was transient and reached a maximum 4 h after irradiation. Such a specific modulation of receptor expression upon uv irradiation might be biologically significant, considering the numerous intercellular recognition phenomena in skin biology. alpha-L-Rhamnose-specific receptor on SCL-1 could not be distinguished from alpha-D-glucose-specific receptor on the basis of neoglycoproteins binding, uptake, and related inhibitions. Lectin expression was mainly detected on the cell surface, and its overexpression due to uv rays required a de novo protein synthesis process.