Abstract 381: Dorsomorphin, A Novel Inhibitor Of Bone Morphogenetic Protein Signaling
Bone morphogenetic protein (BMP) signals regulate developmental patterning, organogenesis, and tissue remodeling. The association of mutations in the BMP type II receptor with idiopathic pulmonary arterial hypertension suggests a critical role in pulmonary vascular biology. Testing the role of BMP signals in pulmonary vascular function has been limited by the lack of pharmacologic tools which selectively target this pathway. We sought to identify small molecule modulators of BMP signaling using a high-throughput in vivo chemical screen. Potential BMP signaling inhibitors were identified by their ability to perturb dorsoventral axis formation in zebrafish embryos, a process that is directed by BMP signaling gradients. Among 7500 molecules screened, one induced dorsalization, the exaggerated development of dorsal structures at the expense of ventral structures, and altered the expression of dorsal and ventral markers pax2.1 and eve1, in a manner consistent with global BMP inhibition in the embryo. Dorsomorphin, as we have called this molecule, inhibited the ability of BMPs 2, 4, 6, and 7 to activate SMAD1/5/8 and induce transcription of Id genes (IC50<0.5 μM) in pulmonary artery smooth muscle cells (PASMCs). Dorsomorphin did not inhibit activation of SMAD2 by TGF-β or Activin A. The selectivity of dorsomorphin for BMP signaling was confirmed by its ability to inhibit the activity of constitutively-active BMP type I receptors, ALK2, ALK3, and ALK6, but not constitutively-active Activin and TGF-β type I receptors, ALK4, ALK5 or ALK7. Importantly, dorsomorphin did not inhibit BMP-mediated activation of MAPK p38, permitting resolution of SMAD-dependent and SMAD-independent signaling. Dorsomorphin inhibited BMP-mediated differentiation of C2C12 cells and PASMCs, measured by the induction of alkaline phosphatase expression, without apparent cytotoxicity. Taken together, these findings suggest that dorsomorphin is a specific inhibitor of BMP type I receptor kinases that can inhibit BMP signaling in a dose and temporally-controlled manner in vivo. Dorsomorphin may have utility in testing the roles of BMP signaling in cellular and animal models of pulmonary vascular function and disease.