Effects of long wave ultraviolet radiation on photosensitizing and related compounds. II

Abstract

The effects of long wave ultraviolet radiation (320-400 nm) on the binding of twenty-five fluorescent photosensitizing and related compounds to the major saline soluble guinea-pig epidermal proteins were studied. Binding before or after irradiation was detected on polyacrylamide disc gel electrophoresis by correlating the fluorescent migration pattern with the amido black counterstained pattern. Effects were seen only on photo-allergic and structurally related compounds (phenothiazines and halogenated salicylanilides). The binding of five phenothiazine derivatives was detected only after irradiation. Ten of twelve halogenated salicylanilides were bound without irradiation, and eleven were bound following it. Ultraviolet exposure appeared to increase the amount of each halogenated salicylanilide that was bound and/or to alter the existing complex.It was previously shown (Alani, 1973) that long wave ultraviolet radiation (320-400 nm), hereafter referred to as UVA, altered the fluorescence and lengthened the persistence of potential photo-allergic compounds in the skin of mice. These findings suggested that there was an association of the compound with some portion of the epidermis. In this investigation we have studied effects of UVA on the in vitro binding of twenty-five fluorescent photosensitizing and related compounds (Pathak, 1969;Hjorth & Fregert, 1968) to the saline soluble proteins of guinea-pig epidermis. MATERIALS AND METHODS Test compoundsA 1% solution (10 mg/ml) of each compound was made in dimethyl sulphoxide (DMSO). The compounds included five phenothiazines, salicylanilide, twelve halogenated salicylanilides (HS), four acridine dyes, and three other chemically dissimilar compoimds (Table i). The 3,3',4',5-tetrachlorosalicylanilide (TCSA) was also used in a i % solution in acetone and in methanol.

Photoallergic contact dermatitis

“…This conjugate is then able to induce and elicit a delayed hypersensitivity response in the skin, leading to the clinical appearance of dermatitis. In vitro studies provided initial evidence that halogenated salicylanilides can bind to γ‐globulin in the presence of daylight (25) and epidermal proteins without, and in the presence of UVA (26). It was further demonstrated that TCSA forms short‐lived reactive intermediates that decay quickly if they do not encounter a protein.…”

Effects of long wave ultraviolet radiation on photosensitizing and related compounds. I

“…If these compoimds are bound to the protein in vivo, as has been shown in vitro (Herman & Sams, 1971;Alani & Dunne, 1973), then the UVA radiation may possibly, through a free radical mechanism, similarly affect all HS compounds and salicylanilide to produce an unstable photoproduct, which must be in apposition to protein carrier at the time of irradiation. This may suggest that halogen atom substitutions and their position in the molecule are probably not essential for the changes observed.…”

“…This may suggest that halogen atom substitutions and their position in the molecule are probably not essential for the changes observed. If these compoimds are bound to the protein in vivo, as has been shown in vitro (Herman & Sams, 1971;Alani & Dunne, 1973), then the UVA radiation may possibly, through a free radical mechanism, similarly affect all HS compounds and salicylanilide to produce an unstable photoproduct, which must be in apposition to protein carrier at the time of irradiation. Or the UVA radiation may alter or activate the skin component(s), facilitating the combination with the altered or imaltered compound(s).…”

“…The action of ultraviolet irradiation on the latter has been suggested to be the formation of free radicals which bind to epidermal protein (Jenkins, Welti & Baines, 1964;Harber, Harris & Baer, 1966), or an action on the compound to produce a stable photoproduct that will act as hapten independent of further irradiation (Burckhardt, 1941;Willis & Kligman, 1968). It has been demonstrated in vitro that 4',5-dibromosalicylanilide and 4'-monobromosalicylanilide are produced by UVA irradiation of 3,4',5-tribromosalicylanilide and 4',5-dibromosalicylanilide respectively, while 4'-monobromosalicylanilide has not been affected by further UVA irradiation (Coxon, Jenkins & Welti, 1965). On the basis of Burckhardt's theory it is suggested that in photosensitization to TBS the 4'-position, and the halogen substituted there, is a key point in the process of photosensitization (Osmundsen, 1969).…”