Inhibition of NF-kappaB and HIV-1 long terminal repeat transcriptional activation by inducible nitric oxide synthase 2 activity.

In the human lymphoblastoid T cell line JJhan-5.1, stably transfected with a human immunodeficiency virus-1 long terminal repeat luciferase vector, the level of luciferase activity is dependent on activation of the nuclear factor kappaB (NF-kappaB) transcription factor. Tumor necrosis factor-induced luciferase activity was not modified in JJhan-5.1 cells co-cultivated with murine adenocarcinoma EMT-6 cells but was strongly decreased when nitric oxide (NO) synthase 2 expression was induced in these cells. Two NO synthase inhibitors counteracted this inhibitory effect. Tumor necrosis factor-alpha binding to JJhan-5.1 cells was not modified after incubation with EMT-6 cells. Viability and protein synthesis in JJhan-5.1 cells were also unchanged. Induction of NF-kappaB DNA binding activity was inhibited when EMT-6 cells expressed NO synthase 2 activity. Aminoguanidine, which completely abolished nitrite production, prevented this inhibition. NF-kappaB activation was also strongly inhibited by S-nitrosoglutathione but was marginally affected by N-(2-aminoethyl)-N-(2-hydroxy-2-nitrosohydrazino)-1, 2-ethylenediamine. Taken together, these results indicated that NO-related species, released by EMT-6 effector cells and probably different from NO itself, inhibited NF-kappaB activation in human lymphoblastoid target cells. Consequently, transcriptional activity of a long terminal repeat-driven luciferase gene construct was markedly diminished.