P.D. Mier

Lysosomal hydrolases of the epidermis. 6. Changes in disease.

The activities of 14 acid hydrolases have been measured in normal and diseased human epidermis. Our findings were as follows: (i) Increased hydrolase activity was common in lesions; the clinically uninvolved skin of patients, however, invariably showed normal values. (2) The pattern of change was independent of the nature of the disease, the arylsulphatases and β‐glucosidase usually showing the greatest elevations. (3) The magnitude of the changes differed from disease to disease, being most marked in the lesions of psoriasis. (4) Ichthyosiform erythroderma was exceptional in showing elevated levels of the galactosidases and cathepsins B, and D. We suggest that (with the exception of ichthyosiform erythroderma) the abnormalities which we have observed may be related to the proliferative rate of the epidermis.

Inhibition of lysosomal enzymes by dapsone

Massive doses of vitamin A lead to excessive degradation of tissue chondroitin sulphate, presumably mediated via the release of lysosomal hydrolases. Barranco (1974) has shown that dapsone (diaminodiphenyl sulphone) prevents.this response, and has speculated that the drug may act by the direct inhibition of lysosomal enzymes. We have therefore investigated the effect of dapsone on fourteen lysosomal hydrolases in vitro. Extracts of guinea-pig epidermis were prepared as before (Mier & van den Hurk, 1975a). Dapsone (generously donated by A.C.F.Chemiefarma, Maarssen, The Netherlands) was dissolved in dimethylsulphoxide (DMSO) at 40 mg/ml, and diluted with water to 400 ̂ g/ml. Further dilutions of 40 /(g/ml and 4 figlml were made using 1% aqueous DMSO. Assay mixtures consisted of o-i ml buffered substrate, 0-05 ml epidermal extract or BSA (reagent blank) and 005 ml dapsone solution or 1% DMSO (control); the individual substrates, reaction conditions and assay techniques have been described previously (Mier & van den Hurk, I975a-c). All measurements were carried out in duplicate. After subtraction of the appropriate reagent blank, inhibition was calculated as a percentage of the activity of the control. No significant inhibition of any enzyme was observed at final dapsone levels of i or 10 /(g/ml. At IOO/(g/ml, six glycosidases and arylamidase were significantly inhibited (Table i). Acid phosphatase (EC 3.I.3.2.), pyrophosphatase (EC 3.1.4.1), arylsulphatases A and B (EC 3.1.6.1), j9-galactosidase (EC 3.2.1.23), cathepsin B, (EC 3.4.4.-) and cathepsin C (EC 3.4.4.9) were unaffected. These findings would, at first sight, appear to support the hypothesis of Barranco (1974). However, difficulties arise when comparing our data with the situation in vivo. In particular, the blood level following a normal therapeutic dose of dapsone is only of the order of 5 /ig/ml (Chang, Wolcott &

ADENOSINE 3': 5'-CYCLIC MONOPHOSPHATE PHOSPHODIESTERASE IN SKIN.: I. MEASUREMENT AND PROPERTIES

Summary.— The degradation of adenosine 3′: 5′‐cyclic monophosphate (cAMP) to adenosine 5′‐monophosphate by a cutaneous phosphodiesterase has been demonstrated for the first time. The ratio of phosphodiesterase: adenyl cyclase activity in skin is the same as that found in liver and brain. Certain properties of the cutaneous enzyme have been studied; in its solubility, pH curve, Km and sensitivity to methylxanthines it seems very similar to cAMP phosphodiesterases of other tissues.

THE ADENYL CYCLASE OE SKIN II. ADENYL CYCLASE LEVELS IN ATOPIC DERMATITIS

Adenyl cyclase activity was measured in biopsy specimens from the lesions of atopic dermatitis, from atopic “uninvolved” skin, and from the skin of healthy controls. No decrease in the level of this enzyme was found in the atopic.

THE ADENYL CYCLASE OF SKIN I. MEASUREMENT AND PROPERTIES

A method is described for the measurement of cutaneous adenyl cyclase. Certain properties of the adenyl cyclase of guinea‐pig skin have been studied; this enzyme appears to be unusual in that no stimulation of its activity by adrenalin could be demonstrated.

EARLIEST DESCRIPTION OF THE ATOPIC SYNDROME

SIR, After the publication of our article Lichen Sclerosus et Atrophicus in the Bantu {British Journal of Dermatology, 91, 81), I have been informed that F.P.Scott and J.G.H.Lups described two cases of Lichen Sclerosus et Atrophicus affecting Bantu patients. Consequently the sentence in paragraph 2, page 82, should be changed to We therefore describe four cases of LSA, one of the most uncommon skin disorders in the Bantu (Scott & Lups, 1971). M.DOGLIOTTI

Acid hydrolases in psoriatic epidermis

This laboratory is currently investigating the levels of acid hydrolase activity in the epidermis of various skin lesions, and our findings will be published in full in due course. The results which we have obtained for psoriasis, however, seem sufficiently remarkable to warrant preliminary publication. Epidermal slices were cut using a keratotome set for a depth of 0-2 mm, frozen in liquid nitrogen, and stored at — 20°C prior to analysis. Specimens were homogenized at 20 mg/ml in bovine serum albumin (i mg/ml), centrifuged, and the activity of fourteen acid hydrolases determined in the supernatant using techniques already described (Mier & van den Hurk, I975a-c). The activity of each enzyme in eight specimens of psoriatic lesion, seven specimens of uninvolved epidermis from psoriatic patients, and thirty-six specimens from healthy controls is shown in Table i. Although there is a tendency for all enzymes to be increased in the lesion (suggesting a greater number of lysosomes in comparison to normal epidermis), it is clear that there are striking and specific increases in the levels ofarylsulphatases A and Band of ^-glucosidase. These enzymes are increased 34fold, 22-fold and 11-fold over the respective mean control values; there is no overlap with the normal range. The values for the uninvolved psoriatic epidermis, by contrast, are identical to the controls. Since lysosomal hydrolases are (at least in some tissues) inducible enzymes, these findings point to the accumulation of a metabolite which contains ;S-glucoside residues and which is sulphated. The most likely candidate, on the rather scanty evidence currently available, seems to be a sulphated glycolipid. These compounds are characteristically located in the plasma membrane, where they may be associated with membrane-bound enzymes (Karlsson, Samuelsson & Steen, 1974). Thus our findings are consistent with, and may be causally related to the defects which have been described in adenyl cyclase (Hsia et al, 1972; Wright et al, 1973; Yoshikawa et al, 1975; Mui, Hsia & Halprin, 1975) and in the membrane-bound ATP hydrolytic activity (Mahrle & Orfanos, 1974) of the psoriatic lesion. The authors wish to thank Professor J.W.H.Mali and the medical staff of this Department for their help in providing the clinical material used in this work.

4. OVERALL PROFILE IN COMPARISON WITH DERMIS AND OTHERTISSUES Lysosomal hydrolases of the epidermis

The activities of fifteen acid hydrolases have been measured in seven tissues of the guinea‐pig; fourteen of these were also assayed in the epidermis of four other mammalian species. The most striking finding was that the proportion of acid phosphatase was consistently much higher in epidermis than in the other tissues investigated.

A lysosomal storage disorder of the epidermis characterized by a deficiency of α-mannosidase and an accumulation of mannose-rich materials

Laboratory investigation of a patient diagnosed as ichthyosiform erythroderma bullosa revealed the following abnormalities:

THE CONTROL OF GLYCOGEN UTILIZATION IN SKIN; PHOSPHORYLASE B KINASE AND PHOSPHORYLASE A PHOSPHATASE

SUMMARY.— The activation of phosphorylase b and the inactivation of phos‐phorylase a by skin homogenates have both been demonstrated for the first time. Certain properties of the enzymes catalysing these reactions (phosphorylase b kinase and phosphorylase a phosphatase, respectively) were investigated; it was concluded that the control system in skin is similar to that of muscle and liver. The possibility of certain dermatoses being associated with defects in this system is discussed.