The objective of the present study was to examine the repressive effect of transforming growth factor beta 1 (TGF-β1) in the regulation of
Npr1
(coding for guanylyl cyclase/natriuretic peptide receptor-A; GC-A/NPRA) gene expression and vascular signaling. The rat thoracic aortic vascular smooth muscle cells (RTASMC) and denuded aortic rings were cultured in Dulbecco’s modified Eagle’s medium containing 10% fetal bovine serum and treated with TGF-β1 in a time-and dose-dependent manner. Treatment with TGF-β1 decreased NPRA mRNA and protein levels by 62% (0.42 ± 0.05 vs. control, 0.9 ± 0.02, p < 0.01) and 55% (9603 ± 860 vs. control, 22211 ± 1449, p < 0.01), respectively. TGF-β1 treatment significantly increased delta EF1 (δEF1) protein expression by 2.4-fold (907.9 ± 36.5. vs. control, 378.5 ± 10.3; p < 0.001) and enhanced its recruitment to
Npr1
promoter. TGF-β1-treated RTASMCs and denuded aortic rings showed significant increases in α-smooth muscle actin (α-SMA) and collagen type 1 alpha 2 (COL1A2) protein expression, which were markedly attenuated by ANP treatments. The TGF-β1-pretreated cells showed 2.6-fold increase in α-SMA (control, 1523 ± 143, TGF-β1, 3997 ± 182 and TGF-β1 + ANP, 2172 ± 135) and 3.4-fold increase in COL1A2 (control, 1250 ± 77, TGF-β1, 4234 ± 110 and TGF-β1 + ANP, 1546 ± 57), respectively. In
ex vivo
experiments of denuded-aortic rings, TGF-β1 decreased
Npr1
mRNA and protein levels by 62% (0.39 ± 0.06 vs. control 1.10 ± 0.01) and 70% (2609 ± 69 vs. control 5775 ± 123), respectively, and significantly (p < 0.0) increased the expression of TGF-β1-responsive proteins, namely α-SMA (2.6-fold) and COL1A2 (3.1-fold). Treatment with increasing concentrations of ANP (IC50=6x10
-9
M), relaxed denuded aortic rings contracted with prostaglandin F2α (PGF2α); however, pretreatment with TGF-β1 significantly attenuated ANP-mediated vascular relaxation after PFG2α contraction (ANP-treated, 68.68 ± 9.4 vs. TGF-β1 + ANP-treated 88.85 ± 4.7). The endothelium-intact vessels were not affected by TGF-β1 incubation. Together, the present results suggest that an antagonistic cascade exists between TGF-β1 pathways and ANP/NPRA signaling, which might be critical in the vascular remodeling and regulation of hypertension and cardiovascular homeostasis.
Exogenous transforming growth factor-β1 enhances smooth muscle differentiation in embryonic mouse jejunal explants
