Time course of 8-methoxypsoralen-induced skin photosensitization in PUVA-bath photochemotherapy

Disseminated Scleroderma of a Japanese Patient Successfully Treated with Bath PUVA Photochemotherapy

Background:

Localized scleroderma is known to be resistant to therapies. Recently, it has been reported that bath PUVA photochemotherapy is effective for treating this dermatosis.

Objectives:

Although according in earlier reports mainly white populations have been treated successfully with bath PUVA therapy, there is little knowledge of whether it is effective in treating colored populations. We treated a 64-year-old Japanese woman suffering from disseminated scleroderma with bath PUVA photochemotherapy to see its effects.

Conclusion:

Although rather high cumulative UVA doses were required for this patient compared with those needed in earlier reports, no adverse effects were observed. The lesions were markedly improved, suggesting that this therapeutic modality is well-tolerated and useful for colored patients such as the Japanese. Furthermore, it turns out that the thermographical assessment is useful to estimate clinical improvement of this sclerosing skin disorder.

Documento de consenso sobre la modalidad terapéutica del baño-PUVA

Bath PUVA is a variant of phototherapy as efficacious as oral PUVA therapy that avoids many of the adverse effects associated to this treatment. Nevertheless, the special features and the specialized equipment required for its employment have limited its application in the dermatologic clinics of our country. Following the trend initiated after the publication of the consensus document on oral PUVA therapy and narrow band (NB) UVB therapy, the Spanish Photobiology Group from the Spanish Academy of Dermatology and Venereology has developed a therapeutic guideline for bath PUVA therapy based on the literature review and the experience of its members. The document aims to be a practical reference guide for those dermatological centres that include phototherapy among their services. It reviews the concept and indications of this type of treatment and proposes recommendations concerning therapeutic procedures, drug associations of interest and prophylaxis and management of adverse effects.

Correlation between 8-methoxypsoralen bath-water concentration and photosensitivity in bath-PUVA treatment

BACKGROUND

Bath-PUVA treatment, originally established in Scandinavia, offers several advantages over oral PUVA and has become increasingly popular in recent years. Outside Scandinavia 8-methoxypsoralen (8-MOP) is the prevailing photosensitizer for this PUVA modality and is used arbitrarily in a wide range of concentrations. Up to the present, data are lacking on the impact of 8-MOP bath-water concentration on UVA dosimetry.

OBJECTIVE

We investigated the influence of increasing 8-MOP bath-water concentrations on photosensitivity in bath-PUVA treatment.

METHODS

Fifteen healthy volunteers without abnormal photosensitivity or recent exposure to ultraviolet radiation were included in an intraindividually controlled comparison study. In all volunteers the minimal phototoxic dose (MPD) was determined on the volar side of their forearms after immersion for 20 minutes in 4 different 8-MOP bath-water concentrations (0.5, 1, 2.5, and 5 mg/L). The correlation between 8-MOP concentration and photosensitivity (defined as the reciprocal value of the MPD) was analyzed by linear regression analysis. In addition, the time course of erythema formation and the UVA dose-erythema response curve was assessed for each psoralen concentration.

RESULTS

The median MPD and the 25%-75% interquartile were 5.7 J/cm(2) (5.7-8), 4 J/cm(2) (4-5.7), 2.8 J/cm(2) (2.8-5.7), and 2 J/cm(2) (2-2.8) at an 8-MOP concentration of 0.5, 1, 2.5, and 5 mg/L, respectively. Linear regression analysis revealed a significant correlation between 8-MOP bath-water concentration and photosensitivity (r = 0.98; P =.019). Bath-PUVA-induced erythema peaked after a median time interval of 3 days, with a range of 2 to 4 days. The slope of the UVA dose-erythema response curve was similar for all psoralen concentrations.

CONCLUSION

UVA dose requirements in bath-PUVA treatment decrease linearly with increasing 8-MOP concentrations. A single MPD assessment at 72 hours after the UVA exposure is inappropriate for accurate determination of the patients' photosensitivity. The hazard of wrong UVA dosimetry is comparable at all psoralen concentrations.

Disseminated scleroderma of a Japanese patient successfully treated with bath PUVA photochemotherapy

BACKGROUND

Localized scleroderma is known to be resistant to therapies. Recently, it has been reported that bath PUVA photochemotherapy is effective for treating this dermatosis.

OBJECTIVES

Although according in earlier reports mainly white populations have been treated successfully with bath PUVA therapy, there is little knowledge of whether it is effective in treating colored populations. We treated a 64-year-old Japanese woman suffering from disseminated scleroderma with bath PUVA photochemotherapy to see its effects.

CONCLUSION

Although rather high cumulative UVA doses were required for this patient compared with those needed in earlier reports, no adverse effects were observed. The lesions were markedly improved, suggesting that this therapeutic modality is well-tolerated and useful for colored patients such as the Japanese. Furthermore, it turns out that the thermographical assessment is useful to estimate clinical improvement of this sclerosing skin disorder.

Guidelines for topical PUVA: a report of a workshop of the British photodermatology group

Psoralen photochemotherapy [psoralen ultraviolet A (PUVA)] plays an important part in dermatological therapeutics, being an effective and generally safe treatment for psoriasis and other dermatoses. In order to maintain optimal efficacy and safety, guidelines concerning best practice should be available to operators and supervisors. The British Photodermatology Group (BPG) have previously published recommendations on PUVA, including UVA dosimetry and calibration, patient pretreatment assessment, indications and contraindications, and the management of adverse reactions.1 While most current knowledge relates to oral PUVA, the use of topical PUVA regimens is also popular and presents a number of questions peculiar to this modality, including the choice of psoralen, formulation, method of application, optimal timing of treatment, UVA regimens and relative benefits or risks as compared with oral PUVA. Bath PUVA, i.e. generalized immersion, is the most frequently used modality of topical treatment, practised by about 100 centres in the U.K., while other topical preparations tend to be used for localized diseases such as those affecting the hands and feet. This paper is the product of a recent workshop of the BPG and includes guidelines for bath, local immersion and other topical PUVA. These recommendations are based, where possible, on the results of controlled studies, or otherwise on the consensus view on current practice.

Psoralen activity and binding sites in melanotic and amelanotic human melanoma cells

The biological activity and specific binding sites of 8-methoxypsoralen (8-MOP) are assayed using two human melanoma cell lines, melanotic SK-Mel 28 and amelanotic C32TG. Long-term (72 hr) treatment with 8-MOP at a concentration of 10(-4)M results in an increase in melanogenesis and a decrease in proliferation, similar in both cell lines. Daily exposure of these cells to ultraviolet A (UVA) irradiation (1.28 mJ/cm(2)) does not enhance the response to the compound. Daily pulse application (30 min daily) of 8-MOP does not promote any response. However, in combination with UVA, 8-MOP pulse treatment becomes as effective as the long-term treatment. A decrease in cell proliferation in the constant presence of 8-MOP is not coupled with apoptosis, since no increase in the number of apoptotic nuclei was observed after the treatment. The flow cytometry indicates that 8-MOP arrests the cells at the G0/G1 phase, irrespective of the presence or absence of UVA light. In view of the lack of epidermal growth factor (EGF) receptors in both cell lines, it is not likely that such an arrest is associated with the down-regulation of EGF receptors by 8-MOP. It is noted that this compound elicits a biphasic cell response, since cell proliferation increases after the first 24-hr treatment, whereas it decreases in the subsequent 48 hr and thereafter. Competition binding assays using 3H-8-MOP disclosed: 1) the specific binding of the compound in both cell lines occurs in the presence or absence of UVA light, and 2) a higher binding rate at low concentrations of the compound is in SK-Mel 28 (72%) rather than C32TG (58%) cells. The competition assays in the presence of UVA suggest a possible occurrence of covalent bindings between psoralen and receptor, as DNA covalent binding accounted to only 3-5% of the total binding in both cell lines.