TRANSCRIPTION FACTOR NF-KAPPA-B IS ACTIVATED BY PHOTOSENSITIZATION GENERATING OXIDATIVE DNA DAMAGES

Reactive oxygen intermediates like hydrogen peroxide (H2O2) have been shown to serve as messengers in the induction of NF-kappa B and, then, in the activation and replication of human immunodeficiency virus (HI V)-1 in human cells. Because H2O2 can be converted into the highly rea ctive OH. at various locations inside the cells, we started to investi gate the generation of Reactive oxygen intermediates by photosensitiza tion. This technique is based on the use of a photosensitizer which is a molecule absorbing visible light and which can be located at variou s sites inside the cell depending on its physicochemical properties. I n this work, we used proflavine (PF), a cationic molecule having a hig h affinity for DNA, capable of intercalating between DNA base pairs. U pon visible light irradiation, intercalated PF molecules oxidize guani ne residues and generate DNA single-strand breaks. In lymphocytes or m onocytes latently infected with HIV-1 (ACH-2 or U1, respectively), thi s photosensitizing treatment induced a cytotoxicity, an induction of N F-kappa B, and a reactivation of HIV-1 in cells surviving the treatmen t. NF-kappa B induction by PF-mediated photosensitization was not affe cted by the presence of N-acetyl-L-cysteine while strong inhibition wa s recorded when the induction was triggered by H2O2 or by phorbol 12-m yristate 13-acetate. Another transcription factor like AP-1 is less ac tivated by this photosensitizing treatment. In comparison with other i nducing treatments, such as phorbol 12-myristate 13-acetate or tumor n ecrosis factor alpha, the activation of NF-kappa B is slow, being opti mal 120 min after treatment. These kinetic data were obtained by follo wing, on the same samples, both the appearance of NF-kappa B in the nu cleus and the disappearance of I kappa B-alpha in cytoplasmic extracts . These data allow us to postulate that signaling events, initiated by DNA oxidative damages, are transmitted into the cytoplasm where the i nactive NF-kappa B factor is resident and allow the translocation of p 50/p65 subunits of NF-kappa B to the nucleus leading to HIV-1 gene exp ression.