ACTIVATION OF THE HUMAN-IMMUNODEFICIENCY-VIRUS PROMOTER BY UVA RADIATION IN COMBINATION WITH PSORALENS OR ANGELICINS

The effects of mono- and bifunctional furocoumarins plus UVA radiation (PUVA and related treatments) on the human immunodeficiency virus-1 (HIV-1) promoter were studied using HeLa cells stably transfected with the chloramphenicol acetyl transferase gene under the control of the HIV-1 promoter. The experiments were performed with three psoralens (5-methoxypsoralen, 5-MOP; 8-methoxypsoralen, 8-MOP; and 4'-aminomethyl-4,8,5'-trimethyl-psoralen, AMT) and four angelicins (angelicin: 4,5'-dimethylangelicin, 4,5'-DMA; 6,4'-dimethylangelicin, 6,4'-DMA; and 4,6,4'-trimethylangelicin, TMA). The drugs alone and UVA radiation alone showed no effect on the HIV promoter. However, when the cells were incubated with the furocoumarins at 0.1-40 mug/mL and then irradiated, the HIV promoter was activated in distinct fluence ranges, i.e. (1) no promoter activity was discernible at low fluences (e.g. at 0.1 mug/mL of 8-MOP up to 100 kJ/m2), (2) as the fluence was increased, the promoter activity increased to reach a maximum (10-50-fold with respect to the unexposed samples), and (3) as the fluence was further increased, the promoter activity decreased. Similar (although shifted on the fluence scale) patterns were observed with either >340-nm UVA radiation or with UVA radiation contaminated with a small amount of UVB radiation (typical for PUVA lamps). The effective fluences were inversely related to the drug concentration. Experiments with 5-MOP and 8-MOP indicated reciprocity of the drug concentration and radiation fluence. The HIV promoter response patterns were similar for monofunctional angelicins and bifunctional psoralens. This indicated that the furocoumarin-DNA cross-links are not a prerequisite for the promoter activation and that the monoadducts suffice to elicit the HIV promoter response. The HIV promoter-activating effectiveness of different drugs correlated with their photosensitizing potential. Thus, among psoralens the effectiveness order was AMT > 5-MOP > 8-MOP, and among angelicins: TMA > 6,4'-DMA > 4,5'-DMA > angelicin. The effectiveness did not vary substantially for 5-MOP, 8-MOP, 4,5'-DMA, and 6,4'-DMA. The combined drug and UVA radiation doses were higher than those that elicit cellular responses or those that may be received by the human white blood cells during extracorporeal PUVA therapy (photopheresis).