The excitation of 8-methoxypsoralen with visible light: reversed phase HPLC quantitation of monoadducts and cross-links.
The formation of 8-methoxypsoralen-DNA monoadducts and cross-links is presumed to be responsible for the efficacy of photochemotherapies that employ 8-methoxypsoralen activated with long-wavelength ultraviolet radiation (UVA, 320-400 nm). In this report it is shown that 8-methoxypsoralen can also be activated with visible light (419 nm). Bovine aorta smooth muscle cells were treated with 8-methoxypsoralen (1,000 ng/mL) and 419 nm light (up to 12 J/cm2). Cellular DNA was isolated, hydrolyzed using nucleolytic enzymes and then analyzed by reversed-phase high-performance liquid chromatography. The primary effect of using visible light instead of long-wavelength ultraviolet radiation is a more than 10-fold reduction in the extent of cross-link formation. Because the extent of monoadduct and cross-link formation has not been routinely measured in experiments in which cellular assays have been performed, it is difficult to correlate cell response to the presence of a particular type of 8-methoxypsoralen photoadduct (monoadduct or cross-link). Thus, the use of visible light allows the study of cells containing nearly 100% monoadducts. In addition, the reduction in cross-link formation when visible light is used to activate the compound may also reduce the mutagenicity of 8-methoxypsoralen and hence enhance its therapeutic efficacy.
Gasparro
F P
FP
Department of Dermatology, Yale University School of Medicine, New Haven, CT 06510.
Gattolin
P
P
Olack
G A
GA
Deckelbaum
L I
LI
Sumpio
B E
BE
D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000032:analysis / Q000528:radiation effects; D066298:In Vitro Techniques; D008027:Light; D008730:Methoxsalen / Q000032:analysis / Q000528:radiation effects*; D009131:Muscle, Smooth, Vascular / Q000737:chemistry / Q000528:radiation effects; D010777:Photochemistry
D004247:DNA; D008730:Methoxsalen