Glucocorticoid effects on contact hypersensitivity and on the cutaneous response to ultraviolet light in the mouse

Changes in skin physiology during bath PUVA therapy

BACKGROUND

Frequent bathing leads to a skin barrier damage with various changes in physiological skin parameters. Conversely, ultraviolet (UV) irradiation may improve the impaired skin barrier by reducing inflammatory reactions.

OBJECTIVES

The aim of this study was to investigate the changes of physiological skin parameters during a therapy with 8-methoxypsoralen (8-MOP) bathing and subsequent UVA irradiation.

METHODS

Thirty patients with a skin disease without barrier disruption were treated with daily bathing in a 8-MOP solution (0.0005%) and subsequent UVA irradiation. Multiple physiological skin parameters (transepidermal water loss, skin blood flow, skin colour, sebum content, skin hydration) were measured repeatedly on clinically non-affected skin on the back, forearm and forehead. In addition, patch testing with sodium lauryl sulphate (SLS) (0.5%) was performed on the forearm and on the back.

RESULTS

We found a moderate but significant disturbance of skin barrier and hydration on the forearm and the back (bathing + irradiation) after increasing dosages of therapy. In addition, SLS testing leads to stronger reactions.

CONCLUSIONS

We conclude that on clinically healthy skin the impairment of skin barrier by frequent bathing cannot be completely compensated by subsequent UVA irradiation. When conducting a treatment with 8-MOP bathing and UVA irradiation a concomitant therapy supporting the recovery of skin barrier, e.g. with moisturizer, should be performed.

Immunological properties of dehydroepiandrosterone, its conjugates, and metabolites

The immunological response to the administration of various C-19 steroids has been of increasing interest. Although the action of dehydroepiandrosterone has been studied, the responses to its metabolites have not been explored. In the present study the ability of dehydroepiandrosterone, its conjugates, and metabolites to oppose the anti-inflammatory action of glucocorticoids on the inflammatory response to 2,4-dinitrochlorobenzene in the sensitized mouse was examined. A clear difference was seen between the antiglucocorticoid activity of dehydroepiandrosterone, its conjugates, and its 5 beta-metabolites on the one hand and the planar 5 alpha- and delta 4-metabolites, which were devoid of antiglucocorticoid activity. The mechanism of this antiglucocorticoid activity remains to be established.

Apparent absence of a benign precursor lesion: implications for the pathogenesis of malignant melanoma

This review relates concepts derived from the study of chemically induced skin cancer in animal models to the pathogenesis of malignant melanoma in humans. Most chemically induced experimental cancers in animals, including melanomas in rodents, arise within a benign precursor lesion. The initiation-promotion-progression sequence is a central concept in animal models for carcinogenesis. Many human melanomas appear to arise from epidermal melanocytes, with no associated precursor lesion. This article considers why there is no apparent precursor in many human melanomas and the consequences of this absence. Melanocyte physiology and factors that govern escape from defenses such as DNA repair, local tissue environment, and immunity presumably influence melanocyte conversion to melanoma. These factors may determine the absence of a precursor lesion in primary melanomas. In addition, it is possible that some human melanomas arise by cellular mechanisms different from those causing cancer in rodent models. Both molecular and prospective clinical studies will be required to explain this apparent paradox in the pathogenesis of melanoma. A similar approach may help to explain the origin of basal cell carcinoma and perhaps other human cancers that appear to arise directly from normal cells. From a clinical point of view, the absence of an identifiable, benign precursor lesion requires even greater emphasis on melanoma prevention. Research on mechanisms of ultraviolet carcinogenesis indicates that appropriate postexposure treatments may be useful in preventing long-term consequences of sunburn, including melanoma.

Actinic DNA damage and the pathogenesis of cutaneous malignant melanoma

The near epidemic of melanoma and non-melanoma skin cancer in the United States and certain other industrialized nations is attributable to cutaneous exposure to sunlight more than to any other factor. Chronic exposure to UV irradiation and a high total cumulative dose may be less deleterious than are periodic bursts of large amounts of sun exposure leading to severe sunburn. Such an exposure pattern is characteristic of individuals such as office workers whose outdoor activities are irregular rather than daily, as with farmers or fisherman. Although UV irradiation is injurious to many cellular elements, the mechanisms underlying UV-mediated skin cancer are thought to be most likely related to DNA damage to cutaneous cells. Various types of UV-induced DNA damage have been identified, and they differ in biologic significance. Damage which is apt to be most cytotoxic is probably less effective as an inducer of skin cancer than is more subtle damage, which is tolerated but can initiate malignant transformation. Repair of DNA damage involves specific cellular activities which vary in their effectiveness in restoring cutaneous cell function to normal. Other biologic effects of UV irradiation may contribute to the development of skin cancer through effects on such defenses as pigmentation and the immune response. Sun-induced damage to DNA, however, is apparently necessary. Biologic consequences of dangerous environmental exposure to UV irradiation can be modulated by changes in life-style, the depth of the ozone layer, use of sunscreens, and possibly by hormones or their synthetic analogs.