Furocoumarin-photosensitized hydroxylation of guanosine in RNA and DNA.

Guanosine hydroxylation was used as a marker for assessing photooxidation of DNA and RNA sensitized by monofunctional and bifunctional furocoumarins. DNA or RNA, treated with sensitizer and UVA light, was enzymatically hydrolyzed, dephosphorylated and then analyzed by reversed-phase HPLC with electrochemical detection. Hydroxylated guanosine, i.e. 8-hydroxy-2'-deoxyguanosine (8-OHdG) or 8-hydroxyguanosine (8-OHG), was quantitated. 3-Carbethoxypsoralen (3-CP) was found to be an efficient photosensitizer for oxidation of guanosine in DNA, resulting in conversion of up to 0.4% of guanosine residues to 8-OHdG. In contrast, dramatically lower levels of guanosine hydroxylation were observed in 3-CP-photosensitized RNA. Psoralen was found to be a more efficient photosensitizer than angelicin in both DNA and RNA. Additional studies of oxidation of 3-CP-photosensitized DNA indicated that double-stranded DNA is 10 times more susceptible to photooxidation than single-stranded DNA, implicating 3-CP binding to DNA as an important mechanistic step in photooxidation of guanosine. The effects of D2O and degassing with argon on photooxidation of guanosine in DNA sensitized by 3-CP were inconsistent with a mechanism involving 1O2. In addition, chelation of adventitious metal ions present in preparations of DNA photosensitized by 3-CP had no effect on hydroxylation of guanosine.

Interleukin 6 induces human immunodeficiency virus expression in infected monocytic cells alone and in synergy with tumor necrosis factor alpha by transcriptional and post-transcriptional mechanisms.

The immunoregulatory cytokine interleukin 6 (IL-6) directly upregulates production of human immunodeficiency virus (HIV) in acutely as well as in chronically infected cells of monocytic lineage. In addition, IL-6 synergizes with tumor necrosis factor alpha (TNF-alpha) in the induction of latent HIV expression. Unlike TNF-alpha, upregulation of viral expression induced by IL-6 alone does not occur at the transcriptional level and it is not associated with accumulation of HIV RNA. However, when IL-6 and TNF-alpha synergistically stimulate HIV production, accumulation of HIV RNA and increased transcription are observed, indicating that IL-6 affects HIV expression at multiple (transcriptional and post-transcriptional) levels.