ABSTRACT
Psoralen photooxidation products (POP products) were obtained by UVA irradiation (365 nm, 180-640 W/m2) of an aqueous psoralen solution with fluences of 0-800 kJ/m2. Preincubation of POP products with glutathione peroxidase (GSHPer) or catalase, as well as presence of catalase during UVA irradiation of the aqueous psoralen solution did not influence their hemolytic activity. However, both GSHPer and catalase inhibited POP-induced conversion of methemoglobin. This indicates that hydrogen peroxide and psoralen peroxides destructible by GSHPer, which are being produced during psoralen photooxidation, do not possess hemolytic activity. Furthermore, hydrogen peroxide does not appear to serve as an intermediate in the process of hemolysin formation. Hydrogen peroxide generated during psoralen photooxidation is apparently the main POP product responsible for MetHb conversion.
Subject(s)
Catalase/metabolism , Erythrocytes/drug effects , Furocoumarins/pharmacology , Glutathione Peroxidase/metabolism , Hemolysis/drug effects , Methemoglobin/drug effects , Ultraviolet Rays , Erythrocytes/physiology , Furocoumarins/chemistry , Furocoumarins/radiation effects , Humans , Kinetics , Oxidation-Reduction , Oxyhemoglobins/drug effectsABSTRACT
The dark and photosensitized (366 nm) hemolytic effects of imperatorin and its photooxidation products, the hydroperoxides I and II as well as the corresponding alcohol of the hydroperoxide I (imperatorin alcohol), were studied on human erythrocytes. Imperatorin was shown to photosensitize hemolysis, its fluence (D) dependence of the rate of photohemolysis (V) followed the equation V = V0 + aD2 + bD1/2, in which V0 is the dark hemolysis rate and a and b are constants. At fluences below 200 kJ/m2, the main hemolytic contribution derives from the bD1/2 component, which is due to the in situ formation of the imperatorin hydroperoxides, while at fluences higher than 200 kJ/m2, the main contribution corresponds to the aD2 component due to the two-photon damage of cell membranes. Hydroperoxides I and II induce oxyhemoglobin cross-linking, as well as its conversion to methemoglobin and hemichrome. These reactions involve hydroxyl and alkoxy radicals, as the hemolysis and oxyhemoglobin conversion could be inhibited by t-butanol and butylated hydrotoluene. For comparison, the dark hemolytic effect of the imperatorin alcohol was approximately 10-fold less than of the hydroperoxides.
Subject(s)
Furocoumarins/pharmacology , Hemolysis/drug effects , Hemolysis/radiation effects , Darkness , Erythrocytes/drug effects , Erythrocytes/metabolism , Erythrocytes/radiation effects , Furocoumarins/chemistry , Humans , In Vitro Techniques , Oxidation-Reduction , Oxyhemoglobins/drug effects , Oxyhemoglobins/metabolism , PhotobiologyABSTRACT
Psoralenes (furocoumarins) in combination with ultraviolet (UV) A radiation (320-400 nm) are used in the treatment of vitiligo, psoriasis, cutaneous T-cell lymphoma and other skin and autoimmune diseases (PUFA therapy). The mechanism of psoralene-photosensitive modification of biologically significant molecules, such as DNA, protein unsaturated lipids, antioxidants, etc. is considered in the paper. Particular emphasis is laid on the mechanism and biomedical significance of photo reactions proceeding via the stage of formation of psoralene photo oxidation products (POP). POP causes oxidative damage to many molecules in in vitro experiments and mediates the T-cell immunity cell in vivo, as appeared as suppression of delayed hypersensitivity and contact sensitivity in mice. The use of randomized double blind control has indicated that POP has therapeutical effects on eczema. A new modality of psoralene photo chemotherapy that consists in the UV-A radiation of psoralene solution followed by its administration (POP therapy) to patients. Unlike conventional PUFA therapy, POP therapy does not require the patients' skin to be exposed to UF-A radiation, which allows adverse effects, such erythema, skin hyperpigmentation, etc. to be avoided.
