THROMBIN REGULATION OF ENDOTHELIN-1 GENE IN ISOLATED HUMAN PULMONARY ENDOTHELIAL-CELLS

Endothelin (ET)-1 is a potent vasoconstrictor elicited from endothelia l cells in response to a variety of stimuli and an important mediator for a variety of vascular diseases including pulmonary hypertension. I n this paper, we describe the molecular regulation of the ET-1 gene in response to a vasoactive mediator, thrombin, in human pulmonary endot helial cells. Thrombin induces preproET-1 mRNA through a transcription ally dependent mechanism, with a peak induction after 1 h of exposure. Analysis of chromatin structure identified several DNase I-hypersensi tive regions under both basal and thrombin-stimulated conditions that reside in the 5'-promoter region, indicating that the ET-1 promoter is a constitutive promoter. Deletion analysis was employed as a function al assay to identify regions of the ET-1 promoter that are important i n transcriptional regulation. We found that sites between -141 and -37 8 bp are essential for basal activity and that those between -378 and -484 bp are essential for thrombin-stimulated activity. However, full expression under both conditions required an element(s) within -952 bp .