Abstract
Background Altered endothelial cell (EC)-derived mediator levels, including increased endothelin-1 (ET-1), are hallmarks of human pulmonary arterial hypertension (PAH). Gene mutations for receptors for bone morphogenic proteins (BMP), or transforming growth factor-β (TGF-β) cause heritable PAH. The effects of BMPs and TGF-β on ET-1 production by human pulmonary microvascular EC (HMVEC-LBl) are unknown. Methods HMVEC-LBl were exposed in-vitro to BMPs 2, 4, and 7 or TGF-β1 in basal or complete medium. ET production was measured, as well as total cellular protein. Levels of Smad 5 and phosphorylated Smads 1/5 were also measured. Results BMP-4 did not increase ET-1 while BMP-2 increased it minimally in basal medium. BMP-7 increased ET-1, but only at 100 ng/ml. By contrast, TGF-β increased ET-1 throughout most of the studied dose range. All BMPs and TGF-β increased levels of phosphorylated Smads 1/5 without depleting levels of Smad 5. Conclusions With the exception of BMP-7 at high-concentrations, the BMPs that interact with BMP receptor 2, the receptor implicated in heritable PAH, do not or minimally modulate in-vitro constitutive ET-1 production by HMVEC-LBl. TGF-β increases ET-1 synthesis, and this may have clinical relevance in PAH.
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