Transcriptional regulation of the human iNOS gene in vascular-smooth-muscle cells and macrophages: evidence for tissue specificity.

We have cloned the 5' upstream -1034 to +88 fragment of the human inducible nitric oxide synthase (hiNOS) gene and demonstrate its competence to promote luciferase gene transcription in vascular-smooth-muscle (VSM) cells and macrophages. Sequential 5' end-deletions localized positive regulatory elements of hiNOS transcription in VSM A7r5 cells downstream of nucleotide -205 and demonstrated the functional importance of the resident NF-kappaB site (nucleotides -115 to -106). The hiNOS promoter/enhancer was induced strongly by LPS and IFN-gamma, and modestly by IL-1beta in RAW 264.7 cells, but not in VSM cells. Truncation of the NF-kappaB site markedly diminished, but did not eliminate, LPS-inducibility. Sodium salicylate and ibuprofen down-regulated the basal transcriptional activity of the hiNOS promoter/enhancer in VSM but not in RAW 264.7 cells. These results indicate that the transcriptional regulation of the hiNOS gene features considerable complexity and tissue specificity.