Metabolism of essential fatty acids by human epidermal enzyme preparations: evidence of chain elongation

The present studies were undertaken in order to delineate the source of human epidermal arachidonic acid, 20:4(n-6). Epidermal microsomal preparations from normal (N) and diseased epidermis (clinically uninvolved (PU) and involved psoriatic (PI) epidermis) were incubated in vitro with either [14C]18:2(n-6), [14C]20:3(n-6) or [14C]malonyl CoA to determine the activities of the delta 6, delta 5 desaturases and elongate, respectively. Experiments were performed in parallel with rat liver microsomal preparations where enzyme activities are well documented. Data derived from the enzymatic assays were compared to fatty acid composition data derived from epidermal total lipids. The enzymatic conversion rates were determined after methylation and separation of the 14C-labeled fatty acid methyl esters by argentation thin-layer chromatography and reverse phase high-performance liquid chromatography. Our data demonstrated: that N, PU, and PI epidermis were all capable of elongating 18:3(n-6) into 14C-labeled 20:3(n-6) via the addition of [14C]malonyl CoA, and this activity was markedly elevated (fivefold) in PI preparations; that N, PU, and PI epidermal preparations lacked the capacity to desaturate 18:2(n-6) and 20:3(n-6); and striking alterations in the individual fatty acids (as weight percent) in the total fatty acids of the PI epidermal extracts when compared to the PU and N extracts. These findings indicate that epidermal arachidonic acid is not biosynthesized locally from tissue linoleic acid and must, therefore, depend on contribution from another endogenous source.

Cytochemical expression of epidermal peroxidase and cytochrome oxidase activities in pathological skin conditions of man

The cytochemical expression of epidermal peroxidase and cytochrome oxidase activity was recently well documented in normal human skin. We report here its expression in basal and squamous cell carcinomas, actinic keratoses, psoriasis, allergic contact dermatitis, seborrheic keratoses, and autosomal dominant ichthyosis vulgaris. The two enzyme activities were evaluated using the diaminobenzidine method. If present, the two enzymes were always localized in the same organelles as in normal epidermis: endogenous peroxidase in the nuclear envelope and endoplasmic reticulum, and cytochrome oxidase in mitochondria. In basal and squamous carcinomas, actinic keratoses and psoriasis, the keratinocytes lost their peroxidase activity, but maintained their cytochrome oxidase activity. In seborrheic keratoses, allergic contact dermatitis and ichthyosis vulgaris, the cytochrome oxidase activity was greatly reduced or abolished in keratinocytes, Langerhans' cells, and melanocytes, whereas the peroxidase activity was present as in normal epidermis. These results indicate that the two peroxidatic enzymes studied are not interrelated and alternatively suppressed by different cellular dysfunctions.

[Biochemical diagnosis of Anderson-Fabry disease in two brothers]

Activity of several lysosomal enzymes was studied in leukocytes, blood plasma and skin fibroblasts of two adult brothers with clinical diagnosis of Fabry disease. Activity of ceramide trihexoside-galactosidase was distinctly decreased in both patients. The residual enzymatic activity constituted 5-6% in the patients leukocytes, less than 10% in blood plasma and 25% in fibroblasts as compared with controls. Differences in composition of alpha-D-galactosidase multiple forms were detected in fibroblasts and blood cells of the patients with Fabry disease as compared with normal leukocytes by means of isoelectric focusing.

Vitamin K-dependent carboxylase in skin

Vitamin K-dependent carboxylase is demonstrated in skin microsomes from humans, rats, rabbits, and mice. This enzyme converts a number of distinct protein-bound glutamic acid residues into gamma-carboxyglutamic acid residues, which strongly interact with Ca++ ions. The enzymatic activity (expressed per mg protein) in skin is about 20% of that in liver. Vitamin K-dependent carboxylase is present in both epidermal and dermal tissue. It is demonstrated that warfarin treatment in mice results in an accumulation of noncarboxylated precursor proteins in both dermal and epidermal microsomes. Most probably this effect of warfarin is not restricted to mice, but occurs also in the skin of patients under oral anticoagulant therapy. A possible relation between vitamin K-dependent skin carboxylase and the gamma-carboxyglutamic acid-containing protein in calcified nodules from patients with scleroderma and dermatomyositis is discussed.

Additive effects of ultraviolet B and crude coal tar on cutaneous carcinogen metabolism: possible relevance to the tumorigenicity of the Goeckerman regimen

The effect of cutaneous exposure to ultraviolet B (UVB) radiation alone, to crude coal tar (CCT) alone, and to the combination of UVB and CCT on the inducibility of the microsomal cytochrome P-450-dependent carcinogen-metabolizing enzyme aryl hydrocarbon hydroxylase (AHH) and other monooxygenases such as 7-ethoxyresorufin O-deethylase (ERD) and 7-ethoxycoumarin O-deethylase (ECD) activities in the skin of neonatal rats was studied. Exposure of the animals to UVB (400-1600 mJ/cm2) alone resulted in a dose-dependent increase in cutaneous enzyme activities. At a UVB dose of 1200 mJ/cm2 increases in AHH, ECD, and ERD were 194%, 115%, and 244%, respectively. A single topical application of CCT (10 ml/kg) 24 h before sacrifice resulted in significant induction of AHH (350%), ECD (921%), and ERD (796%) activities. Treatment of animals with the same dose of CCT followed by UVB exposure resulted in additive and/or synergistic effects on AHH (858%), ECD (1229%), and ERD (1166%) activities in the skin. In contrast, exposure of animals to UVB prior to CCT application had effects no different from those of CCT alone. Epoxide hydrolase and glutathione S-transferase activities in skin from all experimental groups were not different from those of controls. High-pressure liquid chromatographic analysis of the metabolism of benzo[a]pyrene (BP) by cutaneous microsomes prepared from animals treated with UVB alone, CCT alone, and the combination of UVB and CCT revealed increased formation of all the metabolites in each experimental group. The largest increase in metabolite formation occurred in animals receiving CCT followed by UVB exposure. The inducibility of trans-7,8-diol formation by UVB alone and CCT alone was 203% and 435%, respectively, whereas with CCT followed by UVB it was 1065%. The differential responses in AHH activity were found to parallel the capacity of skin microsomal enzymes to enhance the binding of [3H]-BP to DNA. These studies indicate that the sequence of exposure to the components of the Goeckerman regimen in rodents greatly influences metabolic activity in skin. When applied in the same sequence employed in the Goeckerman regimen (CCT followed by UVB exposure) the additive effect upon catalytic activity essential for cancer initiation suggests a possible mechanism for the enhancement of human skin cancer in individuals exposed to this therapeutic regimen.

A rapid and simple test system for the evaluation of the inhibitory activity of retinoids on induced ornithine decarboxylase activity in the hairless rat epidermis

In mouse skin, antiproliferative agents including retinoids inhibit induction of ornithine decarboxylase activity by a variety of hyperproliferative stimuli. In the hairless rat skin, ornithine decarboxylase activity was induced by ten successive strippings with cellotape and by topical application of 12-O-tetradecanoyl-phorbol-13-acetate. Topical application of all trans-retinoic acid (25 nmol/cm2) immediately after the tape stripping of the skin significantly inhibited the induction of ornithine decarboxylase activity at all time points measured. The inhibition by all trans-retinoic acid of ornithine decarboxylase induced by cellotape stripping was dose dependent as was found to be the case for arotinoid, retinol, Ro-10-1670, motretinid, 13-cis-retinoic acid, etretinate, and vitamin A. Oral administration of all trans-retinoic acid also inhibited the ornithine decarboxylase activity induced by cellotape stripping. We propose the assay of ornithine decarboxylase activity in the hairless rat epidermis after tape stripping for a rapid evaluation of new retinoids.

Effect of application frequency on epidermal ornithine decarboxylase induction by chrysarobin in SENCAR mice

Ornithine decarboxylase (ODC EC 4.1.1.17) induction in mouse epidermis after single or multiple topical applications of chrysarobin differed from that following topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA). Following a single application of 220 nmol chrysarobin, ODC activity began to rise at 24 h reaching a peak at 56 h and returned to normal after 96 h. When 5 separate applications of 220 nmol chrysarobin were applied in multiple application protocols, an alteration in the ODC induction response was observed. With a once per week or twice per week application protocol, ODC was elevated in a multiphasic manner giving multiple peaks of activity after the last application. Interestingly, the magnitude of ODC induction was greater using the once per week, compared to the twice per week, application protocol. Preliminary results indicate that a once per week application protocol is more effective than a twice per week protocol for promoting the development of skin papillomas in SENCAR mice. Thus, the magnitude of the induced ODC response with chrysarobin, although low compared to TPA, correlated with tumor promoting activity.

Dopachrome conversion and dopa oxidase activities in recessive yellow mice. Catalytic activities of extracts from pheomelanic and eumelanic tissues

The dopa oxidase activity of tyrosinase and the dopachrome conversion activity of dopachrome oxidoreductase (dopachrome conversion factor) are reduced in skin or hair follicle extracts of pheomelanic mice compared with eumelanic mice. In this study, pheomelanic tissues are compared with eumelanic tissues of the same mice and found to be reduced in their DO and DC activities. Implications are discussed.

Biosynthesis of variant medium chain acyl-CoA dehydrogenase in cultured fibroblasts from patients with medium chain acyl-CoA dehydrogenase deficiency

We prepared monospecific antiserum in rabbits against medium chain acyl-CoA dehydrogenase (MCAD) purified from rat liver and studied the biosynthesis of MCAD in cultured skin fibroblasts from patients with MCAD deficiency using the antibody. Cells were incubated with [35S]methionine. The labeled MCAD was immunoprecipitated using the anti-rat MCAD antiserum and Staphylococcus aureus cells and then analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We first demonstrated that antirat MCAD antibody crossreacted specifically with human MCAD. In 13 MCAD-deficient cell lines tested, the residual MCAD activity ranged from 5-12% of the mean of normal controls, but the variant MCAD in all of these cells was indistinguishable from the normal human MCAD on the basis of molecular size, indicating that MCAD deficiency in all of these patients is most likely due to point mutation(s) in the MCAD gene.

Identification of a chymotrypsin-like proteinase in human mast cells

An antiserum was produced against a chymotryptic proteinase purified from human skin. The antiserum did not cross-react with human leukocyte cathepsin G and elastase, rat mast cell proteinase I, and human skin tryptase. Indirect immunofluorescent staining of frozen skin sections to localize the proteinase showed cytoplasmic staining of cells scattered about the papillary dermis and around blood vessels and appendages. Restaining these sections with toluidine blue revealed that the fluorescently stained cells contained metachromatically staining granules, the major distinguishing feature of mast cells. A similar correlation was found in lung tissue. Ultrastructural studies employing the ferritin bridge technique to immunologically identify the proteinase additionally localized the proteinase to mast cell granules. Biochemical and immunochemical characterization of chymotryptic activity solubilized from isolated human lung mast cells identified a chymotryptic proteinase that may be identical to the skin chymotryptic proteinase. These studies establish that human skin mast cells contain a chymotrypsin-like proteinase that is a granule constituent and provide evidence that indicates a comparable proteinase is also present in lung mast cells.

Chloride-insensitive, glycine-phenylalanine-naphthylamide hydrolysis at neutral pH in human skin fibroblasts

Crude lysosomal preparations from a cultured human skin fibroblast line were found to contain significant levels of a neutral pH hydrolase activity towards glycine--phenylalanine--beta-naphthylamide (NA), a substrate normally used for the assay of lysosomal dipeptidyl aminopeptidase I. However, the activity was chloride ion insensitive, nonlatent, and inhibitable by cationic detergents and amino acids. Assays of substrate selectivity, relative substrate affinity, pH and anion and cation sensitivity indicated the activity to be distinct from dipeptidyl aminopeptidases I (chloride-dependent hydrolysis of Pro-Phe-, Gly-Phe-, Gly-Arg-, and Pro-Arg-NA's at acid pH), II (Lys-Ala-NA hydrolysis), III (Arg-Arg-NA hydrolysis), and IV (Gly-Pro-NA hydrolysis). The lysosomal preparations also contained significant activity towards several amino acid--naphthylamides, notably Arg-NA. Only dipepidyl aminopeptidase I activity showed sensitivity to chloride anions, both dipeptidyl aminopeptidases I and II showed substantial latency, and none of the activities displayed a significant metal cation dependent.

Hyper-induction of skin ornithine decarboxylase activity in psoriatic patients

Ornithine decarboxylase activity was measured in skin from 14 normal and 24 psoriatic subjects (with stable plaque type psoriasis vulgaris) using punch biopsies carried out immediately (0 h) and 6 h after stimulation by cellotape stripping. At 0 h, no significant difference was found between normal and involved or uninvolved psoriatic skin, but a significant increase was measured 6 h after tape stripping. This increase was significantly greater in uninvolved and involved psoriatic skin compared with normal skin. Preliminary results indicated that these changes were localized in the epidermis.

Immunohistochemical study of lysozyme in lupus miliaris disseminatus faciei

The lysozyme activity in tissue samples from patients with lupus miliaris disseminatus faciei (LMDF), sarcoidosis and foreign body granuloma was investigated using the immunoperoxidase technique. The majority of epithelioid cells and giant cells in LMDF and sarcoidosis showed strong lysozyme staining in their cytoplasm. However, most macrophages and giant cells in foreign body granulomas, including granulomatous reactions to epidermal cysts and other foreign materials, stained weakly for lysozyme or were negative. These results suggest that LMDF is different from the foreign body reaction to inert substances, and may be induced by an immunological mechanism associated with cell-mediated immunity.

Regulation of hypoxanthine DNA glycosylase in normal human and Bloom's syndrome fibroblasts

The regulation of the base excision repair enzyme hypoxanthine DNA glycosylase was examined in normal human skin fibroblasts (NHS) and fibroblasts from a patient with Bloom's syndrome. Using randomly proliferating cells and those synchronized at specific intervals in the cell cycle, enzyme levels were shown to become elevated severalfold in a proliferation-associated manner. In NHS synchronized in G0 by serum deprivation or in G1 by isoleucine deprivation, maximal enzyme levels were reached prior to maximal rates of DNA synthesis. In Bloom's syndrome cells synchronized in this manner, these two activities were coincident. Cells synchronized at the G1-S border by hydroxyurea exhibit an initial wave of DNA synthesis upon removal of the drug. The cells then undergo another DNA synthetic cycle climaxing 18-21 h after release. Maximal hypoxanthine glycosylase activity of hydroxyurea-synchronized Bloom's cells was observed during the second round of DNA synthesis. However, in NHS the peak of enzyme activity was observed as early as 9 h prior to the second round of DNA synthesis. To determine if hypoxanthine glycosylase could be induced in the absence of DNA synthesis, serum-synchronized NHS were released in the presence of hydroxyurea. The results showed that inhibition of DNA synthesis did not diminish glycosylase induction which demonstrated that DNA replication was not required for glycosylase induction.

Peroxidase activity in circulating mast cells in blast crisis of chronic granulocytic leukemia. Comparative studies with basophils and cutaneous mast cells

Although the hematopoietic origin of mast cells is very probable, the cell from which they originate is still a matter of speculation. The description of "transitional basophil/mast cells" in myeloproliferative disorders has suggested a common origin for basophils and mast cells. In a case of mast cell transformation of chronic granulocytic leukemia, the authors have studied the morphology and peroxidase activity by three classical technics, of circulating mast cells and transitional "basophil/mast cells." These results were compared with those of blood and bone marrow basophils and those of cutaneous mast cells. In both mast cells and "transitional basophil/mast cells," peroxidase activity was revealed in the nuclear envelope, endoplasmic reticulum, and granules. This activity was detected in unfixed cells and in tannic acid-aldehyde-fixed cells but not in 1.25% glutaraldehyde-fixed cells, where the staining appeared only in the granules. The comparison of this activity with that of normal basophils and mast cells suggests that the proliferating cells in this case possess at the same time the peroxidase activity of basophils and mast cells.

Elastase, a marker for neutrophils in skin infiltrates

The enzyme elastase (EC 3.4.21.37) has proved to be a convenient and extremely sensitive marker for the quantification of neutrophils in cutaneous infiltrates. Fluorometric assay using the synthetic substrate MeOSuc-Ala-Ala-Pro-Val-N-methylcoumarin permitted the measurement of this enzyme in as few as five cells and was linear up to about 1000 cells per sample. The mean activity of lysates of human blood-derived neutrophils was 0.57 +/- 0.08 pmol of 7-amino-4-methyl-coumarin released per hour per neutrophil. Extracts of normal human skin contained no measurable elastase activity but resulted in a slight inhibition of the neutrophil enzyme (mean 12%). Application to the in vivo situation has been demonstrated by the use of leukotriene B4 as chemotactic agent. A reproducible neutrophil infiltrate was found at a dose of 2 ng, well below the threshold for the appearance of microabscesses.

Basal cell carcinoma and collagenase

The interaction of connective tissue stroma and epithelial cutaneous cancer is an active area of investigation in dermatology. Studies summarized here explore the role of collagenase in basal cell carcinoma (BCC) invasiveness. Evidence is presented to support the role of a cytokine or cytokines secreted by BCCs that stimulate collagenase production by surrounding stromal fibroblasts. Prospects for further research in this area are proposed.

Time-dependent biphasic response of aromatase to dexamethasone in cultured human skin fibroblasts

Human genital skin fibroblasts grown in cell culture possess aromatase activity and, therefore, provide a model to investigate the molecular mechanisms that control aromatase in extraglandular tissues. Following the observation by other investigators that glucocorticoids stimulated aromatase activity in cultured stromal-vascular cells from adipose tissue, we examined the influence of dexamethasone (DEX) on aromatase in cultured skin fibroblasts. Preincubation of skin fibroblasts with DEX stimulated aromatase expression in all cell strains. In time-course studies, aromatase activity showed a biphasic curve, with peak levels at 12 h and a return to baseline levels by 72 h. When DEX was removed after 12 h, aromatase activity could be completely restimulated by DEX only after a period of 60-72 h. The DEX stimulation appeared to involve glucocorticoid receptor function, since the concentration of DEX required for half-maximal stimulation of aromatase activity (4.2 nM) was similar to the dissociation constant (Kd, 4.3 nM) of the receptor (for DEX). Actinomycin D and cycloheximide (CHX) inhibited DEX stimulation of aromatase when they were present in the preincubation and assay media. When cells were preincubated with DEX and CHX and then washed free of CHX and DEX before the assay, superinduction of aromatase activity occurred. Our data concerning the time course and superinduction of aromatase activity by DEX are in contrast to the findings reported by others for adipose tissue stromal-vascular cells and suggest that the mechanisms for the control of aromatase in extraglandular tissue may vary significantly in different tissues.

Glucocorticoid-induced vasoconstriction in human skin. An inhibitory role on phospholipase A2 activity

The ability of topically applied betamethasone valerate to reduce erythema produced by a variety of vasodilators was assessed. The steroid significantly reduced the erythema induced by topical arachidonic acid, intradermal histamine, and compound 48/80. We postulated that the steroid reduced endogenous phospholipase activity either before or after application of the vasodilators, or both. This action may explain the mechanism of glucocorticoid-induced vasoconstriction in the skin and part of the steroids' action in acute inflammatory skin disease.

Measurements of 3 alpha,17 beta-androstanediol glucuronide in serum and urine and the correlation with skin 5 alpha-reductase activity

Serum and urinary measurements of 3 alpha,17 beta-androstanediol glucuronide (3 alpha-diol G) reflect peripheral androgen action and have been useful clinically. This study was designed to compare these levels in hirsute women, normal premenopausal and postmenopausal women, and in men and to correlate each measurement with skin 5 alpha-reductase activity (5 alpha-RA), an excellent correlate of androgenicity. Although serum 3 alpha-diol G values were similar in premenopausal and postmenopausal women, values were higher in hirsute women and in men. This pattern was similar for urinary 3 alpha-diol G but with greater overlap in values between hirsute and nonhirsute women and men. Serum 3 alpha-diol G showed a highly significant correlation with levels of genital 5 alpha-RA (r = 0.839, P less than 0.001), whereas urinary 3 alpha-diol G did not correlate. Serum and urinary 3 alpha-diol G also did not correlate with one another (r = 0.03). These data suggest that while both serum and urinary 3 alpha-diol G may be useful clinically, serum 3 alpha-diol G appears to correlate better with androgenicity and 5 alpha-RA. It is suggested further that the sources of serum and urinary 3 alpha-diol G may be somewhat different.

Human lysosomal sphingomyelinase: substrate efficacy of apolipoprotein/sphingomyelin complexes

Human apolipoprotein stimulation of sphingomyelin (SM) hydrolysis by sphingomyelinase from human skin fibroblasts has been studied. Apolipoproteins A-I, A-II, B, C-I, and E do not enhance sphingomyelin hydrolysis above control levels. In contrast, apoC-II stimulates sphingomyelin hydrolysis by approximately 2.5-fold. ApoC-III, the most potent apoprotein activator, stimulates hydrolysis by 3-4-fold. ApoC-III stimulation is not significantly different for the three different isoforms which carry 0, 1, or 2 sialic acid residues. The amino-terminal half of this apoprotein, C-III(1-40), which does not bind to phospholipid surfaces, does not activate sphingomyelinase. In contrast, the carboxyl-terminal half, C-III(41-79), which strongly binds to phospholipid surfaces, stimulates sphingomyelin hydrolysis to the same level as that produced by the intact, full-length apoprotein. Incubation of sphingomyelin vesicles with increasing proportions of apoC-III results in the formation of complexes of increasing apoC-III:SM ratio and decreasing radius. The hydrolysis of sphingomyelin in the 1:50 (mol/mol) complex was more than 2-fold greater than that of the 1:200 (mol/mol) complex. The rate of hydrolysis of egg yolk sphingomyelin in the 1:50 complex was maximal [0.9 mumol h-1 (mg of protein)-1] at the gel----liquid-crystalline phase transition temperature (Tm) of the complex (40 degrees C). The rate of hydrolysis fell markedly at either higher or lower temperature. Determination of the apparent Km and Vmax values below, at, and above Tm indicated that the temperature dependence of sphingomyelin hydrolysis was attributable primarily to changes in Vmax.(ABSTRACT TRUNCATED AT 250 WORDS)

Transport and processing of endocytosed lysosomal alpha-glucosidase in cultured human skin fibroblasts

In the present study we have characterised the molecular products that arise from processing of a precursor form of alpha-glucosidase isolated from urine after endocytosis at 37 degrees C by cultured human skin fibroblasts. The urinary precursor (Mr 110 000) was processed to forms with Mr of 100 000, 80 000 and 74 000. These forms were approximately 4000 Da larger than the corresponding forms of endogenously synthesized alpha-glucosidase. Digestion of the different forms of the enzyme with endoglycosidase F showed that the differences in apparent molecular mass between the exogenous and corresponding endogenous forms were due to difference in glycosylation. Intracellular transport of endocytosed alpha-glucosidase was followed by incubating fibroblast homogenates with glycyl-L-phenylalanine-beta-naphthylamide (Gly-Phe-NH-Nap), which leads to specific lysis of lysosomes. Transport to the lysosomes was a fast process: within 45 min after endocytosis more than 50% of the enzyme was present in the lysosome. The first step in the processing of endocytosed alpha-glucosidase started in a Gly-Phe-NH-Nap-insensitive (prelysosomal) compartment, but further processing of the enzyme to lower-Mr forms was coupled to transport to the lysosomes. Processing of alpha-glucosidase after uptake at 20 degrees C was also studied. At this temperature the enzyme accumulated in an organelle with a low buoyant density, presumably the endosome; this compartment appeared to be heterogeneous, ranging in density from 1.04 g/ml to 1.08 g/ml. Under these conditions only the first step in the processing of the enzyme occurred. It is concluded that endocytosed enzyme is processed more rapidly than endogenously synthesized enzyme owing to the fact that endocytosed enzyme is transported more rapidly to the lysosomes. Furthermore, processing may start in a prelysosomal organelle.