Transcriptional Regulation of the Human iNOS Gene in Vascular-Smooth-Muscle Cells and Macrophages: Evidence for Tissue Specificity

Abstract

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-κB site (nucleotides −115 to −106). The hiNOS promoter/enhancer was induced strongly by LPS and IFN-γ and modestly by IL-1β in RAW 264.7 cells, but not in VSM cells. Truncation of the NF-κB 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.