Transforming growth factor β1 antagonizes the transcription, expression and vascular signaling of guanylyl cyclase/natriuretic peptide receptor A - role of δEF1

The objective of this study was to determine the role of transforming growth factor beta 1 (TGF-beta 1) in transcriptional regulation and function of the guanylyl cyclase A/natriuretic peptide receptor A gene (Npr1) and whether cross-talk exists between these two hormonal systems in target cells. After treatment of primary cultured rat thoracic aortic vascular smooth muscle cells and mouse mesangial cells with TGF-beta 1, the Npr1 promoter construct containing a d-crystallin enhancer binding factor 1 (delta EF1) site showed 85% reduction in luciferase activity in a time-and dose-dependent manner. TGF-beta 1 also significantly attenuated luciferase activity of the Npr1 promoter by 62%, and decreased atrial natriuretic peptide- mediated relaxation of mouse denuded aortic rings ex vivo. Treatment of cells with TGF-beta 1 increased the protein levels of delta EF1 by 2.4-2.8-fold, and also significantly enhanced the phosphorylation of Smad 2/3, but markedly reduced Npr1 mRNA and receptor protein levels. Over-expression of delta EF1 showed a reduction in Npr1 promoter activity by 75%, while deletion or site-directed mutagenesis of delta EF1 sites in the Npr1 promoter eliminated the TGF-beta 1-mediated repression of Npr1 transcription. TGF-beta 1 significantly increased the expression of a-smooth muscle actin and collagen type I alpha 2 in rat thoracic aortic vascular smooth muscle cells, which was markedly attenuated by atrial natriuretic peptide in cells over-expressing natriuretic peptide receptor A. Together, the present results suggest that an antagonistic cascade exists between the TGF-beta 1/Smad/delta EF1 pathways and Npr1 expression and receptor signaling that is relevant to renal and vascular remodeling, and may be critical in the regulation of blood pressure and cardiovascular homeostasis.